Band2play is a free programm that converts chords, eg: (Am, D7, B7b9) to a MIDI Playback file. It's a very simple programm with a powerful conversion engine programmed by Christoph Schröder.
You can chose a lot of different backing styles, like Jazz, Latin Jazz, Pop, ...
You may use it as a generator for playalongs for jazz standarts and improvisation, for singing, for generating any playback you want. You just need the chords.