There are a number of solutions out there for you in order of increasing cost:
1. Get an electronics repair person to add an earphone jack. They’re usually configured so that when you plug in the earphones, the speaker cuts out, and when you remove the earphone plug, the speaker is connected. This is the simplest solution; probably the least expensive one, but the sounds will still be Chordovox sounds.
2. Some years back, a guy had designed a DIY kit for converting a Chordovox to midi. I don’t remember all the details, but since it was publicized in the old Yahoo groups and they have been taken over by groups.io, you may want to start there. What I do remember about this kit is that it still relied on the under-key contacts of the Chordovox and these sometimes corrode.
3. Check out the thread in this forum about Scarff Midi for accordions.
4. Have a midi kit from Master Productions or MusicTech (or one of several other brands) installed by an accordion technician who performs this service. This solution and perhaps number 3, above, will eliminate the under-key contacts in favor of more modern Hall-Effect detectors. In addition, the kits installed by accordion technicians may include bellows pressure transducers for better expression.
5. It may sound a bit snobby on my part, but since Chordovox parts may become increasingly difficult to obtain, you may want to consider buying a new or used Roland accordion.
