Instead of playing instruments for each measure could a setting be added to have the app simply speak the chord number along with a metronome beat? This would be good for practicing for jam sessions.
You mean the app would call out the chord when it changed (or perhaps just before)?
There’s an experimental metronome feature, in case you weren’t aware: here’s how to enable it. (It will be leaving experimental status next year.) It doesn’t announce chords, though.
I’d like to hear more about why you want the chord numbers called out, when they’re already there on the screen…