A
double reed instrument which was invented in the mid-1800s by
Pierre Louis Gautrot. In appearance it strikes one more as an unreeded
brass instrument, looking like a stretched-out trumpet or a slideless
trombone, with its upward-facing bell and rectangularly curled-up tubing; but closer inspection reveals the reeds in the mouthpiece at the side, and the complicated set of keys and levers characteristic of reeded instruments rather than the valves you'd get with a trumpet.
The instrument was originally intended for use in military marching bands, as a rival for Adolphus Sax's recently invented saxophone, but, in its various forms, it has since been used in classical music (for example in Igor Stravinsky's Threni) and in jazz (for example by Sidney Bechet, who solos on it in Mandy Make up Your Mind, which he recorded with the Clarence Williams Blues Five). It's also used by ex-Bonzo Dog Band member Vivian Stanshall on his remarkable Sir Henry at Rawlinson End, where it has a charmingly reedy, puffy, and be-whiskered sound, and is used to particularly good effect in his bizarre and surreal peep inside the mind of 'self-styled encyclopaedia' Reg Smeeton.
After Gautrot patented it in 1856, naming it after a french bandleader named Sarrus, who he credits with the idea (French Patent #28034) Sax thought it was too similar to his own new instrument, and sued the inventor more than once. While the fingering closely resembles that on a saxophone in some respects, the sarrusophone doesn't have a single octave key, but has instead 2 or 3 separate octave keys, enabling the player to reach up into the third octave without the special 'palm-keys' that a saxophone has. It was effective in military bands because you could get lower notes for less weight - the EEb contrabass model is less heavy than a baritone sax, and considerably lighter than the equivalent contrabass sax. Perhaps for this reason, the US Army made a purchase of 148 of them in 1928.
The instrument comes in several flavours, from the EEb contrabass (which goes down to the second Db below the bass clef - an octave lower than a baritone sax) to soprano models - the only sarrusophones to have an unbended sound-tube - which has more or less the same range as a soprano sax. There are always an odd number of bends, 3 in the tenor model, 5 in the baritone and contrabass, so that the bell-shaped end (where the sound comes out) always points upwards.
Information from:
http://www.contrabass.com/pages/sarrus.html
which looks like an excellent starting point for those wanting to know more about the instrument.