Contra octave
The octave range from contra C to contra B, notated C₁–B₁.
What it means
The contra octave is the name for the range from contra C to contra B in the German pitch-naming system, which distinguishes octaves by capitalisation and subscript numbers. It lies an octave below the great octave and therefore covers very low pitches.
In the notation
In German notation the pitches of the contra octave are usually written C₁, D₁, E₁ and so on, occasionally with a prime mark instead of a subscript. In the international scientific pitch notation this range corresponds roughly to C2 through B2.
Musical use
The contra octave is the lowest range reached by standard orchestral instruments: the double bass, contrabassoon and the lowest organ registers extend into it, while a concert grand piano only begins with the sub-contra A below it. The contra octave differs from the great octave, which lies an octave higher and roughly matches the range of the cello or the pianist's left hand in a middle position.