Somewhat off-color, but I sometimes think about "Phantasia," which is an orchestral suite for Phantom with a different instrument representing each character...
I would love to see that for a Sondheim show, and Night Music would suit it because there are a lot of characters with a variety of voice types...
Desiree would be an oboe, Henrik a cello (obviously!), Anne could be a flute, Petra would be a viola, Mme Armfeldt a bassoon, Frederick a clarinet...somebody help me compose this. Hah!
https://newplayexchange.org/users/99643/amanda-delalla