clarinet pitched a fourth lower than the ordinary B♭ clarinet, probably invented in about 1770 by A. and M. Mayrhofer of Passau, Bavaria. The name derives from its basset (“small bass”) pitch and its original curved-horn shape (later supplanted by an angular form). Its bore is narrower than that of the E♭ alto clarinet, and it has a downward extension of compass to the low F of the bass voice (written as C). The boxwood instrument is usually built to order, in straight form with upturned bell.

Though primarily a German instrument, it was known in Paris by 1774 as a contre-clarinette and in London by 1789 as a clara voce. It was employed notably by W.A. Mozart but had practically vanished by 1850. It was revived by Richard Strauss (Elektra, 1st performed 1909).