Vintage Roland synth controller

Cox Electronics have produced ‘The Interpreter’ - “a small box which can be connected between any MIDI controller and a Roland JX-8P, alpha Juno1, alpha Juno2, HS-10, HS-80, MKS-50, MKS-70 or MKS-80 synthesizer.”

It effectively turns MIDI control change messages into System Exclusive (SysEx) messages, the only type that these older Roland synths understood.

Found via Gear Junkies