Jailhouse Rock: An Oral History.

Spider Murphy:

'Little Joe, the trombonist in the 'Prison Band,' actually had a fair amount of professional training. He could really play. I think he might even have studied at a conservatory. Anyway, someone grabbed his trombone and beat him unconscious with it. Then the guy proceeded to just kind of shout the word 'tromboner' into mouthpiece throughout the remainder of the riot.'"

See other accounts of this impromptu rock -n- roll shindig here.

Edit: It appears that the link is dead. Perhaps it will reappear.