How about Spotify on an iPhone and a Bose Audio system?
Oh, is this a live Jazz band? 50 yards is pretty far for a wireless audio system.
Similar to rockstar-nots suggestion; Use a guitar wireless system. The body pack "transmitter" rigged up with adaptors to the tape out jacks on the main mixer. The receiver antenna box connected to a second audio system in the lobby.


Does the noise in your head bother me ?