The contrabassoon or double bassoon is a larger version of the bassoon sounding an octave lower. Its technique is similar to its smaller cousin but the instrument offers more resistance in every way. This stubbornness increases with descending pitch. Its size often requires it to be held with a strap or on an endpin.

Tonally, the contrabassoon sounds much like the bassoon except for a distinctive 'buzz' which becomes almost a clatter in the extreme low range. While prominent in solo situations, this extraneous sound is completely subsumed in the sound of doubling instruments, for which the contrabassoon supplies a solid underpinning.

Composers have often used the contrabassoon to comical or sinister effect by taking advantage of its clumsiness and its sepulchral rattle, respectively. Clear examples of its sound can be heard in Paul Dukas' Sorcerer's Apprentice and Gunther Schuller's concerto for the instrument.