Welcome! On the continuo playback point you mentioned, a practical workaround is to make a separate playback copy of the score and write out a simple right-hand realization for the harpsichord there. Keep your intended bass line, and start with just one short section or cadence before doing all 18 parts. That lets you hear the harmonic support without having to make a fully realized keyboard part compulsory in the performers’ score. For checking the counterpoint, try playing the bass with just one vocal line at a time, then add the other voices. In MuseScore Studio’s Mixer (F10), you can Solo more than one instrument together. Temporarily reducing reverb can also make entries and note endings easier to check; restore it afterwards for the listening version. The controls are documented here: https://handbook.musescore.org/sound-and-playback/mixer These are suggestions for the mock-up you described, rather than a verdict on the composition. A short excerpt with the continuo realized would make it easier for readers to discuss the harmony you actually intend.