BOSS  Dr Synth  DS 330  Sound Module.

Adds around 128 new voices and sounds to your keyboard via MIDI.

Great fun box despite its lack of sophistication.

Has MIDI  IN / OUT / THRU connections and connects to a sound system via 2 x 1/4"  jack sockets.

Comes complete with power supply module and printed version of the pdf file instruction book.

I also have a DR660 Drum machine - see my other items,