"Xas" is a Yannis Xenakis rare piece for a saxophone quartet, composed and created in 1987 in Lille by the Raschèr Quartett.
The title is an anagram of SAX to create a mirror image. One also might note a play on the name of XenAkiS. This is also the only piece Xenakis wrote for the saxophone.
The composer briefly uses new techniques: some quarter tones and simple multiphonics (almost clarinets' broken sounds) punctuate the piece; on the contrary, most "attack modes" and tone colors are absent or left to the performer's choice.
Over time, one might even consider this piece as the first “serious piece" that was written by a major composer for this type of ensemble.
Here is a version played in an empty swimming pool by the "Contemporary music class of Bordeaux Conservatory" conducted by Marie-Bernadette Charrier.