Slippy Thompson and his Twelve Tom-Cats

Hep swing group from the 1945 film The Horn Blows at Midnight. They're playing a club gig for WWII swing-shift workers. Protagonist trumpeter Athanael gets a chance to join the group, but when his playing is booed for being too square, he's swiftly ejected from the establishment.

Band leader Slippy plays the clarinet, and is played by Larry Rio.