Leland Stanford Junior University is a private research university in Stanford, California. Stanford is known for its academic strength, proximity to Silicon Valley, ranking as one of the world's top universities; the university was founded in 1885 by Leland and Jane Stanford in memory of their only child, Leland Stanford Jr. who had died of typhoid fever at age 15 the previous year. Stanford was a U. S. Senator and former Governor of California who made his fortune as a railroad tycoon; the school admitted its first students on October 1, 1891, as a coeducational and non-denominational institution. Stanford University struggled financially after the death of Leland Stanford in 1893 and again after much of the campus was damaged by the 1906 San Francisco earthquake. Following World War II, Provost Frederick Terman supported faculty and graduates' entrepreneurialism to build self-sufficient local industry in what would be known as Silicon Valley; the university is one of the top fundraising institutions in the country, becoming the first school to raise more than a billion dollars in a year.
The university is organized around three traditional schools consisting of 40 academic departments at the undergraduate and graduate level and four professional schools that focus on graduate programs in Law, Medicine and Business. Stanford's undergraduate program is the most selective in the United States by acceptance rate. Students compete in 36 varsity sports, the university is one of two private institutions in the Division I FBS Pac-12 Conference, it has gained the most for a university. Stanford athletes have won 512 individual championships, Stanford has won the NACDA Directors' Cup for 24 consecutive years, beginning in 1994–1995. In addition, Stanford students and alumni have won 270 Olympic medals including 139 gold medals; as of October 2018, 83 Nobel laureates, 27 Turing Award laureates, 8 Fields Medalists have been affiliated with Stanford as students, faculty or staff. In addition, Stanford University is noted for its entrepreneurship and is one of the most successful universities in attracting funding for start-ups.
Stanford alumni have founded a large number of companies, which combined produce more than $2.7 trillion in annual revenue and have created 5.4 million jobs as of 2011 equivalent to the 10th largest economy in the world. Stanford is the alma mater of 30 living billionaires and 17 astronauts, is one of the leading producers of members of the United States Congress. Stanford University was founded in 1885 by Leland and Jane Stanford, dedicated to Leland Stanford Jr, their only child; the institution opened in 1891 on Stanford's previous Palo Alto farm. Despite being impacted by earthquakes in both 1906 and 1989, the campus was rebuilt each time. In 1919, The Hoover Institution on War and Peace was started by Herbert Hoover to preserve artifacts related to World War I; the Stanford Medical Center, completed in 1959, is a teaching hospital with over 800 beds. The SLAC National Accelerator Laboratory, established in 1962, performs research in particle physics. Jane and Leland Stanford modeled their university after the great eastern universities, most Cornell University and Harvard University.
Stanford opened being called the "Cornell of the West" in 1891 due to faculty being former Cornell affiliates including its first president, David Starr Jordan. Both Cornell and Stanford were among the first to have higher education be accessible and open to women as well as to men. Cornell is credited as one of the first American universities to adopt this radical departure from traditional education, Stanford became an early adopter as well. Most of Stanford University is on one of the largest in the United States, it is located on the San Francisco Peninsula, in the northwest part of the Santa Clara Valley 37 miles southeast of San Francisco and 20 miles northwest of San Jose. In 2008, 60% of this land remained undeveloped. Stanford's main campus includes a census-designated place within unincorporated Santa Clara County, although some of the university land is within the city limits of Palo Alto; the campus includes much land in unincorporated San Mateo County, as well as in the city limits of Menlo Park and Portola Valley.
The academic central campus is adjacent to Palo Alto, bounded by El Camino Real, Stanford Avenue, Junipero Serra Boulevard, Sand Hill Road. The United States Postal Service has assigned it two ZIP Codes: 94305 for campus mail and 94309 for P. O. box mail. It lies within area code 650. Stanford operates or intends to operate in various locations outside of its central campus. On the founding grant: Jasper Ridge Biological Preserve is a 1,200-acre natural reserve south of the central campus owned by the university and used by wildlife biologists for research. SLAC National Accelerator Laboratory is a facility west of the central campus operated by the university for the Department of Energy, it contains the longest linear particle accelerator in the world, 2 miles on 426 acres of land. Golf course and a seasonal lake: The university has its own golf course and a seasonal lake, both home to the vulnerable California tiger salamander; as of 2012 Lake Laguni
Yamaha Corporation is a Japanese multinational corporation and conglomerate with a wide range of products and services, predominantly musical instruments and power sports equipment. It is the world's largest piano manufacturing company; the former motorcycle division became independent from the main company in 1955, forming Yamaha Motor Co. Ltd, although Yamaha Corporation is still the largest shareholder. Nippon Gakki Co. Ltd. was established in 1887 as a piano and reed organ manufacturer by Torakusu Yamaha in Hamamatsu, Shizuoka prefecture and was incorporated on October 12, 1897. The company's origins as a musical instrument manufacturer are still reflected today in the group's logo—a trio of interlocking tuning forks. After World War II, company president Genichi Kawakami repurposed the remains of the company's war-time production machinery and the company's expertise in metallurgical technologies to the manufacture of motorcycles; the YA-1, of which 125 were built in the first year of production, was named in honour of the founder.
It was a 125cc, single cylinder, two-stroke, street bike patterned after the German DKW RT125. In 1955, the success of the YA-1 resulted in the founding of Yamaha Motor Co. Ltd. splitting the motorcycle division from the company. In 1954 the Yamaha Music School was founded. Yamaha has grown to become the world's largest manufacturer of musical instruments, as well as a leading manufacturer of semiconductors, audio/visual, computer related products, sporting goods, home appliances, specialty metals and industrial robots. In 1988, Yamaha shipped the world's first CD recorder. Yamaha purchased Sequential Circuits in 1988, it bought a majority stake of competitor Korg in 1987, bought out by Korg in 1993. In the late 1990s, Yamaha released a series of portable battery operated keyboards under the PSS and the PSR range of keyboards; the Yamaha PSS-14 and PSS-15 keyboards were upgrades to the Yamaha PSS-7 and were notable for their short demo songs, short selectable phrases, funny sound effects and distortion and crackly sounds progressing on many volume levels when battery power is low.
In 2002, Yamaha closed down its archery product business, started in 1959. Six archers in five different Olympic Games won gold medals using their products, it acquired German audio software manufacturers from Pinnacle Systems. In July, 2007, Yamaha bought out the minority shareholding of the Kemble family in Yamaha-Kemble Music Ltd, Yamaha's UK import and musical instrument and professional audio equipment sales arm, the company being renamed Yamaha Music U. K. Ltd in autumn 2007. Kemble & Co. Ltd, the UK piano sales & manufacturing arm was unaffected. On December 20, 2007, Yamaha made an agreement with the Austrian Bank BAWAG P. S. K. Group BAWAG to purchase all the shares of Bösendorfer, intended to take place in early 2008. Yamaha intends to continue manufacturing at the Bösendorfer facilities in Austria; the acquisition of Bösendorfer was announced after the NAMM Show in Los Angeles, on January 28, 2008. As of February 1, 2008, Bösendorfer Klavierfabrik GmbH operates as a subsidiary of Yamaha Corp.
Yamaha Corporation is widely known for their music teaching programme that began in the 1950s. Yamaha electronics have proven to be successful and respected products. For example, the Yamaha YPG-625 was awarded "Keyboard of the Year" and "Product of the Year" in 2007 from The Music and Sound Retailer magazine. Other noteworthy Yamaha electronics include the SHS-10 Keytar, a consumer-priced keytar which offered MIDI output features found on much more expensive keyboards. Other companies in the Yamaha group include: Bösendorfer Klavierfabrik GmbH, Austria. Yamaha Motor Company Yamaha Fine Technologies Co. Ltd. Yamaha Golf Cart Company Yamaha Livingtec Corporation Yamaha Metanix Corporation Yamaha Music Communications Co. Ltd. Yamaha Pro Audio Kandō is a Japanese word used by Yamaha Corporation to describe their corporate mission. Kandō in translation describes the sensation of profound excitement and gratification derived from experiencing supreme quality and performance; some reasonable English synonyms are "emotionally touching" or "emotionally moving".
The Yamaha Music Foundation is an organization established in 1966 by the authority of the Japanese Ministry of Education for the purpose of promoting music education and music popularization. It continued a program of music classes begun by Yamaha Corporation in 1954. Yamaha expanded into product groups; the first venture into each major category is listed below. 1897 Keyboard instruments 1903 Furniture 1914 Harmonicas 1922 Audio equipment 1942 Guitars 1955 Yamaha Motor Company 1959 Sporting goods 1959 Music schools 1961 Metal alloys 1965 Band instruments 1967 Drums 1971 Semiconductors 1984 Industrial robots 2001 Yamaha Entertainment Group 2010 Applications Yamaha announced the singing synthesizer Vocaloid for the first time at the German fair Musikmesse on March 5–9, 2003. Yamaha began to get involved with the sale and production of Vocaloid applications themselves with Lily being the first, their involvement continued
Digital signal processor
A digital signal processor is a specialized microprocessor, with its architecture optimized for the operational needs of digital signal processing. The goal of DSP is to measure, filter or compress continuous real-world analog signals. Most general-purpose microprocessors can execute digital signal processing algorithms but may not be able to keep up with such processing continuously in real-time. Dedicated DSPs have better power efficiency, thus they are more suitable in portable devices such as mobile phones because of power consumption constraints. DSPs use special memory architectures that are able to fetch multiple data or instructions at the same time. Digital signal processing algorithms require a large number of mathematical operations to be performed and on a series of data samples. Signals are converted from analog to digital, manipulated digitally, converted back to analog form. Many DSP applications have constraints on latency. Most general-purpose microprocessors and operating systems can execute DSP algorithms but are not suitable for use in portable devices such as mobile phones and PDAs because of power efficiency constraints.
A specialized digital signal processor, will tend to provide a lower-cost solution, with better performance, lower latency, no requirements for specialised cooling or large batteries. Such performance improvements have led to the introduction of digital signal processing in commercial communications satellites where hundreds or thousands of analog filters, frequency converters and so on are required to receive and process the uplinked signals and ready them for downlinking, can be replaced with specialised DSPs with a significant benefits to the satellites' weight, power consumption, complexity/cost of construction and flexibility of operation. For example, the SES-12 and SES-14 satellites from operator SES, both intended for launch in 2017, were built by Airbus Defence and Space with 25% of capacity using DSP; the architecture of a digital signal processor is optimized for digital signal processing. Most support some of the features as an applications processor or microcontroller, since signal processing is the only task of a system.
Some useful features for optimizing DSP algorithms are outlined below. By the standards of general-purpose processors, DSP instruction sets are highly irregular. Both traditional and DSP-optimized instruction sets are able to compute any arbitrary operation but an operation that might require multiple ARM or x86 instructions to compute might require only one instruction in a DSP optimized instruction set. One implication for software architecture is that hand-optimized assembly-code routines are packaged into libraries for re-use, instead of relying on advanced compiler technologies to handle essential algorithms. With modern compiler optimizations hand-optimized assembly code is more efficient and many common algorithms involved in DSP calculations are hand-written in order to take full advantage of the architectural optimizations. Multiply–accumulates operations used extensively in all kinds of matrix operations convolution for filtering dot product polynomial evaluation Fundamental DSP algorithms depend on multiply–accumulate performance FIR filters Fast Fourier transform Instructions to increase parallelism: SIMD VLIW superscalar architecture Specialized instructions for modulo addressing in ring buffers and bit-reversed addressing mode for FFT cross-referencing Digital signal processors sometimes use time-stationary encoding to simplify hardware and increase coding efficiency.
Multiple arithmetic units may require memory architectures to support several accesses per instruction cycle Special loop controls, such as architectural support for executing a few instruction words in a tight loop without overhead for instruction fetches or exit testing Saturation arithmetic, in which operations that produce overflows will accumulate at the maximum values that the register can hold rather than wrapping around. Sometimes various sticky bits operation modes are available. Fixed-point arithmetic is used to speed up arithmetic processing Single-cycle operations to increase the benefits of pipelining Floating-point unit integrated directly into the datapath Pipelined architecture Highly parallel multiplier–accumulators Hardware-controlled looping, to reduce or eliminate the overhead required for looping operations In engineering, hardware architecture refers to the identification of a system's physical components and their interrelationships; this description called a hardware design model, allows hardware designers to understand how their components fit into a system architecture and provides to software component designers important information needed for software development and integration.
Clear definition of a hardware architecture allows the various traditional engineering disciplines to work more together to develop and manufacture new machines and components. Hardware is als
The modular synthesizer is a type of synthesizer, which exists in both physical and virtual forms, consisting of separate specialized modules. The modules are not hardwired together by the manufacturer but are connected together with patch cords, a matrix patching system, or switches by the user to create a patch; the output from the modules may function as control voltages, or logic/timing conditions. Typical modules are oscillators, amplifiers/gates and Envelope generators; the basic modular functions are: signal, logic/timing. Inputs and outputs are an electric voltage; the difference between a synthesizer module and a effects unit is this: the effects unit will have sockets for input and output of the audio signal and knobs or switches for the musician to control various parameters of the device. Modules with the same basic functions may have different inputs and controls, depending on their degree of complexity; some examples include the Voltage Controlled Oscillator, which may have options for sync, linear or exponential frequency modulation, variable waveshape.
Examples of more complex modules include the frequency shifter and vocoder. There are some standards which manufacturers followed for their range of physical synthesizers, such as 1V/octave control voltages, gate / trigger thresholds providing general compatibility. In the past, modular synthesizers were bulky and expensive. Due to the continuously variable nature of knobs and sliders, reproducing an exact patch can be difficult or next to impossible. In the late 1970s, modular synthesizers started to be supplanted in pop music by integrated keyboard synthesizers, racks of MIDI-connected gear, samplers. However, there continued to be a community who chose the physically patched approach, the flexibility and the sound of traditional modular systems. Since the late 1990s, there has been a resurgence in the popularity of analog synthesizers aided by physical standardization practices, an increase in'retro' gear and interest, decreased production costs and increased electronic reliability and stability, the rediscovered ability of modules to control things other than sound, a heightened education through the development of virtual synthesis systems such as MAX/MSP, Pd and Reaktor etc.
Modules can be categorized as either sources or processors Some standard modules found on any modular synthesizer are: Sources - characterized by an output, but no signal input. In its basic form these may be simple waveforms, however these can be dynamically changed through such controls as sync, frequency modulation, self-modulation. Noise source - A source that outputs a random voltage. Common types of noise offered by modular synthesizers include white and low frequency noise. LFO - A low-frequency oscillator may or may not be voltage-controlled, it may be operated with a period anywhere from a fortieth of a second to several minutes. It is used as a control voltage for another module. For example, modulating a VCO will produce frequency modulation, may create vibrato, while modulating a VCA will produce amplitude modulation, may create tremolo, depending on the control frequency; the rectangular wave can be used as a logic / timing / trigger function. EG - An envelope generator is a transient voltage source.
A trigger in the presence of a gate, applied to an envelope generator produces a single, shaped voltage. Configured as ADSR it provides a transient voltage that rises and falls, it can be triggered by a keyboard or by another module in the system that produces a rising trigger in the presence of a gate. It controls the amplitude of a VCA or the cutoff frequency of a VCF, but the patchable structure of the synthesizer makes it possible to use the envelope generator to modulate other parameters such as the frequency or pulse width of the VCO. Simpler EGs or more complex are sometimes available. Sequencer sometimes called an Analog Step Sequencer, is a family of compound module types which may be a source or a processor, see below; as a source, depending upon the configuration, it may produce a sequence of voltages set by adjusting values on front panel knobs. The sequencer may output a trigger, and/or gate, at each step. Sequencers are stepped by a trigger being applied to the trigger input. Designs may allow for stepping forwards or backwards, oscillating patterns, random order, or only using a limited number of stages.
An example of an analog sequencer and controller with this level of complexity is the Doepfer A-154, A-155 combination. Processors - characterized by a signal input and an output.
In physics, sound is a vibration that propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the reception of such waves and their perception by the brain. Humans can only hear sound waves as distinct pitches when the frequency lies between about 20 Hz and 20 kHz. Sound waves above 20 kHz is not perceptible by humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges. Acoustics is the interdisciplinary science that deals with the study of mechanical waves in gases and solids including vibration, sound and infrasound. A scientist who works in the field of acoustics is an acoustician, while someone working in the field of acoustical engineering may be called an acoustical engineer. An audio engineer, on the other hand, is concerned with the recording, manipulation and reproduction of sound. Applications of acoustics are found in all aspects of modern society, subdisciplines include aeroacoustics, audio signal processing, architectural acoustics, electro-acoustics, environmental noise, musical acoustics, noise control, speech, underwater acoustics, vibration.
Sound is defined as " Oscillation in pressure, particle displacement, particle velocity, etc. propagated in a medium with internal forces, or the superposition of such propagated oscillation. Auditory sensation evoked by the oscillation described in." Sound can be viewed as a wave motion in air or other elastic media. In this case, sound is a stimulus. Sound can be viewed as an excitation of the hearing mechanism that results in the perception of sound. In this case, sound is a sensation. Sound can propagate through a medium such as air and solids as longitudinal waves and as a transverse wave in solids; the sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium; as the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure and displacement of the medium vary in time.
At an instant in time, the pressure and displacement vary in space. Note that the particles of the medium do not travel with the sound wave; this is intuitively obvious for a solid, the same is true for liquids and gases. During propagation, waves can be refracted, or attenuated by the medium; the behavior of sound propagation is affected by three things: A complex relationship between the density and pressure of the medium. This relationship, affected by temperature, determines the speed of sound within the medium. Motion of the medium itself. If the medium is moving, this movement may increase or decrease the absolute speed of the sound wave depending on the direction of the movement. For example, sound moving through wind will have its speed of propagation increased by the speed of the wind if the sound and wind are moving in the same direction. If the sound and wind are moving in opposite directions, the speed of the sound wave will be decreased by the speed of the wind; the viscosity of the medium.
Medium viscosity determines the rate. For many media, such as air or water, attenuation due to viscosity is negligible; when sound is moving through a medium that does not have constant physical properties, it may be refracted. The mechanical vibrations that can be interpreted as sound can travel through all forms of matter: gases, liquids and plasmas; the matter that supports the sound is called the medium. Sound cannot travel through a vacuum. Sound is transmitted through gases and liquids as longitudinal waves called compression waves, it requires a medium to propagate. Through solids, however, it can be transmitted as transverse waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and rarefaction, while transverse waves are waves of alternating shear stress at right angle to the direction of propagation. Sound waves may be "viewed" using parabolic objects that produce sound; the energy carried by an oscillating sound wave converts back and forth between the potential energy of the extra compression or lateral displacement strain of the matter, the kinetic energy of the displacement velocity of particles of the medium.
Although there are many complexities relating to the transmission of sounds, at the point of reception, sound is dividable into two simple elements: pressure and time. These fundamental elements form the basis of all sound waves, they can be used to describe, in every sound we hear. In order to understand the sound more a complex wave such as the one shown in a blue background on the right of this text, is separated into its component parts, which are a combination of various sound wave frequencies. Sound waves are simplified to a description in terms of sinusoidal plane waves, which are characterized by these generic properties: Frequency, or its inverse, wavelength Amplitude, sound pressure or Intensity Speed of sound DirectionSound, perceptible by humans has frequencies from abou
The Kronos is a music workstation manufactured by Korg that combines nine different synthesizer sound engines with a sequencer, digital recorder, effects, a color touchscreen display and a keyboard. Korg's latest flagship synthesizer series at the time of its announcement, the Kronos series was announced at the winter NAMM Show in Anaheim, California in January 2011. Much like Kronos' predecessor and Korg's previous flagship synthesizer workstation, the OASYS, Kronos is a custom software synthesizer running on an Intel x86 processor and operating system based on the Linux kernel with RTAI extensions; the Kronos X was introduced in July 2012 with OS version 2 and the Kronos 2 with OS version 3 was announced in November 2014. Updated versions have more memory and new factory sounds, but otherwise have similar hardware based on the Intel Atom processor series, so older models can be upgraded to the newer specs with user-installable OS updates and sound banks. Like its predecessor, the OASYS, the Kronos has multiple sound engines: 1) The SGX-1 Premium Piano sound engine uses continuous stereo piano samples sampled at eight velocity layers per key to produce a Steinway-styled "German Grand" or Yamaha-styled "Japanese Grand" acoustic grand piano.
The samples are directly streamed from the internal solid state drive by using VMT. This synth engine didn't exist on Korg Oasys. With the release of Kronos 2, SGX-2 Premium Piano superseded the SGX-1 sound engine. SGX-2 adds modeled string resonance and support for soft pedal samples and 12 velocity layers per key, making possible a new Bechstein-styled "Berlin Grand" soundset, factory installed on the Kronos 2. Older Kronos models receive an OS update. 2) The EP-1 MDS Electric Piano sound engine offers four models based on specific classic Rhodes electric pianos and two based on Wurlitzer pianos, with software control over hammers, tines and mechanical noise elements. It simulates amplifiers, cabinets and effects associated with those historic electric pianos; this synth engine didn't exist on Korg Oasys. 3) The CX-3 Tonewheel Organ engine is carried over from the Korg CX-3 modeled tonewheel organ released in 2001. The CX-3 engine models a classic tonewheel organ, including rotary speaker effects and chorus effects, tube amplifier.
Nine hardware sliders on the Kronos' control panel function as organ drawbar controllers. This synth engine first appeared on Korg Oasys. A significant upgrade to this engine was made in November 2013 with OS 2.1 which improved both the organ model and the Leslie speaker simulation, was accompanied by two extra banks of organ patches. 4) The HD1 High Definition Synthesizer, which Korg first introduced in the OASYS, uses sample-based synthesis and wave sequencing to generate sounds from the multisamples stored on an internal solid state drive. The capacity of the built-in preset PCM ROM is 314 MB. 5) The MS-20EX Legacy Analog Collection models an expanded version of the original Korg MS-20 semi-modular monophonic analog synthesizer released in 1978. This engine is an update to the version released by Korg in their "Legacy Collection" software, it is found on Korg Oasys as part of the LAC-1 engine. 6) The PolysixEX Legacy Analog Collection models an expanded version of the 6-voice Korg Polysix analog synthesizer produced by Korg from 1982-3.
Similar to the MS-20EX, this engine is an update to the version in Korg's "Legacy Collection" software, can be found on Korg Oasys as part of the LAC-1 engine. 7) The AL-1 Analog Synthesizer models analog subtractive synthesis, with a range of modeled oscillator waveforms, hard sync, analog-style FM, ring modulation. This is another sound engine passed down from the Korg Oasys. 8) The MOD-7 Waveshaping VPM Synthesizer is capable of classic FM sounds and has import compatibility with Yamaha DX7 SysEx formatted sounds. The MOD-7 engine combines Variable Phase Modulation, ring modulation, subtractive synthesis, modular patching to create a wider range of sounds than would have been possible on a classic Yamaha DX-series synthesizer; this synth engine first appeared on Korg Oasys. 9) The STR-1 Plucked Strings engine creates sounds derived from the physical properties of struck or plucked string sounds. This sound engine is well-suited for creating sounds like guitar and clavinet, bell sounds, as well as other sounds based on the physics of a plucked string but not directly related to any known instrument.
The STR-1 was first released as an expansion to the Korg Oasys. There are 61-, 73-, 88-key versions of the Kronos, with the latter two employing graded hammer action keys, the former synth action keys; the Kronos has a 16-track MIDI sequencer combined with a 16-track 24-bit audio recorder. The recorder can record up to four tracks simultaneously. 197 effect types are available. They can be applied as 12 insert effects, 2 master effects, & 2 total effects. In addition to these effects, a separate 3-band EQ for each track is available. Kronos features the Kay Algorithmic Realtime Music Architecture, or KARMA, a complex arpeggiator that generates complex musical phrases in realtime based on the input of a performer. KARMA first appeared in the Korg KARMA keyboard workstation. Kronos has full sample editing functionality. Sample import and export are supported. Import sample formats supported include Korg, Akai
The drum is a member of the percussion group of musical instruments. In the Hornbostel-Sachs classification system, it is a membranophone. Drums consist of at least one membrane, called a drumhead or drum skin, stretched over a shell and struck, either directly with the player's hands, or with a percussion mallet, to produce sound. There is a resonance head on the underside of the drum tuned to a lower pitch than the top drumhead. Other techniques have been used to cause drums to make sound, such as the thumb roll. Drums are the world's oldest and most ubiquitous musical instruments, the basic design has remained unchanged for thousands of years. Drums may be played individually, with the player using a single drum, some drums such as the djembe are always played in this way. Others are played in a set of two or more, all played by the one player, such as bongo drums and timpani. A number of different drums together with cymbals form the basic modern drum kit. Drums are played by striking with the hand, or with one or two sticks.
A wide variety of sticks are used, including wooden sticks and sticks with soft beaters of felt on the end. In jazz, some drummers use brushes for a smoother, quieter sound. In many traditional cultures, drums are used in religious ceremonies. Drums are used in music therapy hand drums, because of their tactile nature and easy use by a wide variety of people. In popular music and jazz, "drums" refers to a drum kit or a set of drums, "drummer" to the person who plays them. Drums acquired divine status in places such as Burundi, where the karyenda was a symbol of the power of the king; the shell always has a circular opening over which the drumhead is stretched, but the shape of the remainder of the shell varies widely. In the Western musical tradition, the most usual shape is a cylinder, although timpani, for example, use bowl-shaped shells. Other shapes include a frame design, truncated cones, goblet shaped, joined truncated cones. Drums with cylindrical shells can be open at one end, or can have two drum heads, one head on each end.
Single-headed drums consist of a skin stretched over an enclosed space, or over one of the ends of a hollow vessel. Drums with two heads covering both ends of a cylindrical shell have a small hole somewhat halfway between the two heads. Exceptions include the African slit drum known as a log drum as it is made from a hollowed-out tree trunk, the Caribbean steel drum, made from a metal barrel. Drums with two heads can have a set of wires, called snares, held across the bottom head, top head, or both heads, hence the name snare drum. On some drums with two heads, a hole or bass reflex port may be cut or installed onto one head, as with some 2010s era bass drums in rock music. On modern band and orchestral drums, the drumhead is placed over the opening of the drum, which in turn is held onto the shell by a "counterhoop", held by means of a number of tuning screws called "tension rods" that screw into lugs placed evenly around the circumference; the head's tension can be adjusted by tightening the rods.
Many such drums have six to ten tension rods. The sound of a drum depends on many variables—including shape, shell size and thickness, shell materials, counterhoop material, drumhead material, drumhead tension, drum position and striking velocity and angle. Prior to the invention of tension rods, drum skins were attached and tuned by rope systems—as on the Djembe—or pegs and ropes such as on Ewe drums; these methods are used today, though sometimes appear on regimental marching band snare drums. The head of a talking drum, for example, can be temporarily tightened by squeezing the ropes that connect the top and bottom heads; the tabla is tuned by hammering a disc held in place around the drum by ropes stretching from the top to bottom head. Orchestral timpani can be tuned to precise pitches by using a foot pedal. Several factors determine the sound a drum produces, including the type and construction of the drum shell, the type of drum heads it has, the tension of these drumheads. Different drum sounds have different uses in music.
For example, the modern Tom-tom drum. A jazz drummer may want drums that are high pitched and quiet whereas a rock drummer may prefer drums that are loud and low-pitched; the drum head has the most effect on. Each type of drum head has its own unique sound. Double-ply drumheads dampen high frequency harmonics because they are heavier and they are suited to heavy playing. Drum heads with a white, textured coating on them muffle the overtones of the drum head producing a less diverse pitch. Drum heads with central silver or black dots tend to muffle the overtones more, while drum heads with perimeter sound rings eliminate overtones; some jazz drummers avoid using thick drum heads, preferring single ply drum heads or drum heads with no muffling. Rock drummers prefer the thicker or coated drum heads; the second biggest factor that affects drum sound is head tension against the shell. When the hoop is placed around the drum head and shell and tightened down with tension rods, the tension of the head can be adjusted.
When the tension is increased, the amplitude of the sound is reduced and the frequency is increased, making the pitch higher and the volume lower. The type of shell affects the sound of a drum; because the vibrati