Thinking out loud about the following:
There exist a near infinite number of musical instruments.
If you have these present in your tags, such as "piano: Sviatoslav Richter" that is useful to see who is playing a certain instrument.
And, if you would like to filter or search by instrument, you could use 'piano' to find certain pianists in your library.
Or if you are in the mood for some cello, filter by 'cello'.
The keyboard player might be listed as playing harpsichord. Or Fender Rhodes. Or synthesizer. Or electric piano. Or grand piano.
The same goes for a saxophone player. He might play alto saxophone, or tenor saxophone, etc.
A singer might be 'just a singer', or a soprano, or a counter-tenor, or throat-singer, or 'spoken-word', etc.
For the purpose of filtering it would be useful to have some main categories for instruments.
Similar to the existing MusicBee feature of genre categories. (Bebop falls under Jazz, etc.)
So we would then have a limited and defined number of main instrument categories such as e.g.:
soprano, tenor, lead vocals, backing vocals, spoken word, ...
piano, grand piano, fortepiano, harpsichord, ...
Fender Rhodes, Wurlitzer, synthesizer, Hammond organ, ...
acoustic guitar, Spanish guitar, baroque guitar, ...
electric guitar, Gibson Les Paul, Fender Stratocaster, ...
tambourine, cowbell, conga, triangle, cabasa, cajon, ...
I am aware this is much more complicated than 'genres', and will be difficult to make useful because it depends on many other factors, such as tagging schemes, the use and implementation of 'performer' tags, etc.
I am curious if other users are interested in such, possibly assemble some useful input and ideas about this, and see if it might be feasible to perhaps make some proposal for.
This might be a good time to address this, since it might influence or be dependent on some other changes that are being proposed or considered, such as the handling of classical music, possible changes to the tagging panel, handling of 'performer' tags, etc.