What is the Sexophonist in Brave New Word? BNW Chapter 5, Part 1

From the text:

The electric sky-signs effectively shut off the outer darkness. "CALVIN STOPES AND HIS SIXTEEN SEXOPHONISTS." From the facade of the new Abbey the giant letters invitingly glared. "LONDON'S FINEST SCENT AND COLOUR ORGAN. ALL THE LATEST SYNTHETIC MUSIC."

The Sixteen Sexophonists were playing an old favourite: "There ain't no Bottle in all the world like that dear little Bottle of mine." Four hundred cou- ples were five-stepping round the polished floor.