The clarinets in B flat and A are the average orchestral devices. The higher, shriller E flat clarinet is also a band tool and is used sometimes in the orchestra. Of the larger clarinets, the B flat bass clarinet is essentially the most critical. The E flat alto and the E flat contrabass clarinets are mainly band gadgets. Clarinets were once made in other keys, but all of those contraptions are now obsolete. The basset horn, a type of alto clarinet, was much utilized by Mozart and was revived by Richard Strauss. The clarinet is a transposing device. See F. G. Rendall, The Clarinet 3d rev. ed.