A rare Ebay post for me!

“The JLCooper “ChromaFace” MIDI retrofit for the Chroma was produced in the 1980s. From the product sheet:

The MIDI Chromaface is a 4 1/2 by 6 inch box that is powered by an included wall transformer. Also included is a 25 conductor cable to plug between Chromaface and Chroma or Chroma Expander. Information exchange includes: Note On/Off commands; Velocity information; After-touch (from MIDI to Chroma only, and only on newest revision of Chroma software); Pitch Bend; Modulation; Program Change; Split keyboard functions by sending/receiving on two channels. The Chromaface may be set to operate on any MIDI channel. List Price: [US] $350. Available 8/84.

See the manual for more information. A schematic is also available here.

Thanks to Christopher Now for the following pictures.”

:::