Bass Clarinets

Like the more common soprano B♭ clarinet, the bass clarinet is usually pitched in B♭ (meaning it is a transposing instrument on which a written C sounds as B♭), but it plays notes an octave below the soprano B♭ clarinet.[1] Bass clarinets in other keys, notably C and A, also exist, but are very rare (in contrast to the regular A clarinet, which is quite common in classical music). Bass clarinets regularly perform in orchestras, wind ensembles/concert bands, occasionally in marching bands, and play an occasional solo role in contemporary music and jazz in particular (source).