This key was at first added to allow easy transposition of parts for the pretty rare bass clarinet pitched in A, but it now finds significant use in live performance band and other literature. A huge difference among soprano and bass clarinet key work is a key pad played by the left hand index finger with a vent which could be exposed for bound high notes. This allows a form of "half hole" fingering that permits notes in higher
registers to be played on the instrument. Newer models generally only have one. The second register key makes the altissimo range much easier to play. As with all wind units, the upper limit of the range is dependent upon the best of the device and capability of the clarinetist. This gives the bass clarinet a usable range of over four
octaves, quite near the variety of the bassoon; indeed, many bass clarinetists perform works at first meant for bassoon or cello because of the plethora of literature for those two gadgets and the shortage of solo works for the bass clarinet. The bass clarinet has been constantly utilized in scoring for orchestra and concert band because the mid 19th century, becoming more common during the middle and latter a part of the twentieth century. A bass clarinet is not always called for in orchestra music, but is nearly always called for in live performance band music. In recent years, the bass clarinet has also seen a beginning to be repertoire of solo literature adding compositions for the instrument alone, or observed by piano, orchestra, or other ensemble. It also is utilized in clarinet choirs, marching bands, and in film scoring, and has played a minor, but power, role in jazz.