What's Bass Saxophone....

The bass saxophone is the second largest existing member of the saxophone family (not counting the subcontrabass tubax). It is similar in design to a baritone saxophone, but it is larger, with a longer loop near the mouthpiece. Unlike the baritone, the bass saxophone is not commonly used. While some composers did write parts for the instrument through the early twentieth century (such as Percy Grainger in Lincolnshire Posy), the bass sax part in today's wind bands is usually handled by the tuba, or in jazz and other popular-music bands by the double bass or electric bass, all of which have a lower range. In the 1920s, the bass saxophone was often used in early jazz recordings, since it was at that time much easier to record compared to the tuba or double bass.
The instrument was first used in 1844 by Hector Berlioz, in an arrangement of his Chant sacre, as well as in the opera Le Dernier Roi de Juda by Georges Kastner, also in 1844. Leonard Bernstein used a bass saxophone in his original score and movie of West Side Story, and the American composer Warren Benson has championed the use of the instrument in his music for concert band.
Although originally available in either B♭ or C (the latter for orchestral use), the modern bass saxophone is pitched in B♭, a perfect fourth lower than the baritone, and thus similar in register to the B♭ contrabass clarinet. Music for bass sax is written in treble clef, just as for the other saxophones, but it sounds two octaves and a major second lower than written. Like the other members of the saxophone family, the lowest written note is B♭ below the staff — for bass saxophone, this note is a concert A♭ in the first octave (~ 51.9 Hz).
The lowest existing member of the saxophone family used to be the rare (and massive) contrabass, pitched in E♭, a perfect fifth lower than the bass. Inventor Adolphe Sax had a patent for a subcontrabass saxophone (or bourdon saxophone), but he apparently never built a fully functioning instrument. Recently some custom–built subcontrabass saxophones have been made by the German instrument maker Benedikt Eppelsheim, sounding an octave lower than the bass saxophone.
Adolphe Sax, the saxophone's inventor, first exhibited the bass saxophone in C at an exhibition in Brussels in 1841. The bass saxophone thus has the distinction of having been the first saxophone to be presented to the public.
http://en.wikipedia.org/wiki/Bass_Saxophone