The contrabass trombone is the lowest-pitched instrument in the trombone family of brass instruments. While modern instruments are pitched in 12 ft F with a single slide, the first practical contrabass trombones appeared in the mid-19th century built in 18′ B♭ an octave below the tenor trombone with a double slide. German opera composer Richard Wagner notably called for this instrument in his Der Ring des Nibelungen opera cycle in the 1870s, and contrabass trombone has since appeared occasionally in large orchestral works without becoming a permanent member of the modern orchestra.

The pitch of a brass instrument corresponds to the lowest playable resonance frequency of the open instrument. The combined resonances resemble a harmonic series. The fundamental frequency of the harmonic series can be varied by adjusting the length of the tubing using the instrument's valve, slide, key or crook system, while the player's embouchure, lip tension and air flow serve to select a specific harmonic from the available series for playing. The fundamental is essentially missing from the resonances and is impractical to play on most brass instruments, but the overtones account for most pitches.