In sound recording and reproduction, audio mixing is the process of combining multitrack recordings into a final mono, stereo or surround sound product. In the process of combining the separate tracks, their relative levels are adjusted and balanced and various processes such as equalization and compression are applied to individual tracks, groups of tracks, the overall mix. In stereo and surround sound mixing, the placement of the tracks within the stereo field are adjusted and balanced. Audio mixing techniques and approaches vary and have a significant influence on the final product. Audio mixing techniques depend on music genres and the quality of sound recordings involved; the process is carried out by a mixing engineer, though sometimes the record producer or recording artist may assist. After mixing, a mastering engineer prepares the final product for production. Audio mixing may be performed on digital audio workstation. In the late 19th century, Thomas Edison and Emile Berliner developed the first recording machines.
The recording and reproduction process itself was mechanical with little or no electrical parts. Edison's phonograph cylinder system utilized a small horn terminated in a stretched, flexible diaphragm attached to a stylus which cut a groove of varying depth into the malleable tin foil of the cylinder. Emile Berliner's gramophone system recorded music by inscribing spiraling lateral cuts onto a vinyl disc. Electronic recording became more used during the 1920s, it was based on the principles of electromagnetic transduction. The possibility for a microphone to be connected remotely to a recording machine meant that microphones could be positioned in more suitable places; the process was improved when outputs of the microphones could be mixed before being fed to the disc cutter, allowing greater flexibility in the balance. Before the introduction of multitrack recording, all sounds and effects that were to be part of a record were mixed at one time during a live performance. If the recorded mix wasn't satisfactory, or if one musician made a mistake, the selection had to be performed over until the desired balance and performance was obtained.
With the introduction of multi-track recording, the production of a modern recording changed into one that involves three stages: recording and mixing. Modern mixing emerged with the introduction of commercial multi-track tape machines, most notably when 8-track recorders were introduced during the 1960s; the ability to record sounds into separate channels meant that combining and treating these sounds could be postponed to the mixing stage. In the 1980s, home recording and mixing became more efficient; the 4-track Portastudio was introduced in 1979. Bruce Springsteen released the album Nebraska in 1982 using one; the Eurythmics topped the charts in 1983 with the song "Sweet Dreams", recorded by band member Dave Stewart on a makeshift 8-track recorder. In the mid-to-late 1990s, computers replaced tape-based recording for most home studios, with the Power Macintosh proving popular. At the same time, digital audio workstations, first used in the mid-1980s, began to replace tape in many professional recording studios.
A mixer is the operational heart of the mixing process. Mixers offer a multitude of inputs, each fed by a track from a multitrack recorder. Mixers have 2 main outputs or 8. Mixers offer three main functionalities. Summing signals together, done by a dedicated summing amplifier or, in the case of a digital mixer, by a simple algorithm. Routing of source signals to external processing units and effects. On-board processors with equalizers and compressors. Mixing consoles can be intimidating due to the exceptional number of controls. However, because many of these controls are duplicated, much of the console can be learned by studying one small part of it; the controls on a mixing console will fall into one of two categories: processing and configuration. Processing controls are used to manipulate the sound; these can vary in complexity, from simple level controls, to sophisticated outboard reverberation units. Configuration controls deal with the signal routing from the input to the output of the console through the various processes.
Digital audio workstations can perform many mixing features in addition to other processing. An audio control surface gives a DAW the same user interface as a mixing console; the distinction between a large console and a DAW equipped with a control surface is that a digital console will consist of dedicated digital signal processors for each channel. DAWs can dynamically assign resources like digital audio signal processing power, but may run out if too many signal processes are in simultaneous use; this overload can be solved by increasing the capacity of the DAW. Outboard gear and audio plug-ins can be inserted into the signal path to extend processing possibilities. Outboard gear and plugins fall into two main categories: Processors – these devices are connected in series to the signal path, so the input signal is replaced with the processed signal. Examples include dynamic processing. However, some processors are used in parallel, as is the case in techniques such as parallel compression/limiting and sidechain equalization.
Effects – these can be considered as any unit that has an effect upon the signal, the term is used to describe units that are connected in parallel to the signal
Alphacoronaviruses are the first of the four genera, Alpha-, Beta-, Gamma-, Deltacoronavirus in the subfamily Coronavirinae of the family Coronaviridae. Coronaviruses are enveloped, positive-sense, single-stranded RNA viruses that include both human and zoonotic species. Within this subfamily, viruses have spherical virions with club-shaped surface projections and a core shell; the name is from the Latin corona, meaning crown, which describes the appearance of the projections seen under electron microscopy that resemble a solar corona. This genus contains what were considered phylogroup 1 coronaviruses. Both the Alpha- and Betacoronavirus lineages descend from the bat gene pool; the virion is enveloped and spherical measuring 120–160 nm in diameter and a core shell of about 65 nm. Glycoproteins and trimers form large surface projections which create the appearance of solar corona from which it takes its name; the genome is positive-sense, single-stranded RNA with a length of 27 to 29 kilobases and a 3’-polyA tail.
Two large, overlapping ORFs at the 5'-end of the genome encode the major non-structural proteins expressed as a fusion protein by ribosomal frameshift. These include regions with helicase and RNA polymerase motifs. There are 7 other genes downstream; these are expressed from a 3'-coterminal nested set of subgenomic mRNAs. This genus, like other coronaviruses, has a spike protein with a type II fusion machine and a receptor-binding domain, it assembles into a trimer. Unlike beta- and gammacoronaviruses, this protein is not cleaved into two halves. Both types of Alphacoronavirus 1, feline coronavirus and canine coronavirus, are known to exist in two serotypes. Serotype II targets Aminopeptidase N; the difference is due to a different spike protein. There is a common ancestor for FCoV and CCoV; this ancestor evolved into FCoV I and CCoV I. An S protein from an unknown virus was recombined into the ancestor and gave rise to CCoV II. CCoV II once again recombined with FCoV to create FCoV II. CCoV II evolved into TGEV.
A spike deletion in TGEV creates PRCV. All these viruses are sorted into the subgenus Tegacovirus. Order Nidovirales Family Coronaviridae Subfamily Coronavirinae Genus Alphacoronavirus. Transmissible gastroenteritis coronavirus Betacoronavirus Coronavirus RNA virus http://viralzone.expasy.org/all_by_protein/766.html
TSS Roebuck was a cargo vessel built for the Great Western Railway in 1925. TSS Roebuck was built by Swan Hunter and Wigham Richardson as one of a pair of new cargo vessels, the other being Sambur, launched on 24 March 1925, she was put to work on freight services between the Channel Islands and Weymouth. In May 1940 she took part in the Dunkirk evacuation, making one trip to the beachhead and evacuating 600 men, including many injured. In June she was sent with her sister ship Sambur to Saint-Valery-en-Caux to assist in the evacuation of the 51st Highland Division. However, by the time they arrived the Germans were in control of the port and both ships were damaged by gunfire. In October 1940 she was requisitioned by the Admiralty for use as a barrage balloon vessel in the Thames and around northern France and renamed Roebuck II, she returned to railway service after the war and resumed operation at Weymouth and in 1948 was taken over by British Railways. In November 1964 she was disguised as the Norwegian SS Galtesund for The Heroes of Telemark.
She continued in service until 27 February 1965, was scrapped the same year