On the bottom of RT picker you can filter quite a few things, but the process is a bit unintuitive and not sequential.

I believe you have some valid points here most were brought up before. I strongly support sorting by Instrument Family type (guitar, piano, harmonica etc) That, in my view should be #1 column in the picker which would double as filter. Because in 99% of cases you already have an idea of what type of instrument you will be selecting.