Short answer: Yes. (borrowed from
@bholder )
Long answer:
I would absolutely count drums. Because drummers can count!! And a lot of singers who've never played an instrument have no concept of rhythm. That's maybe a thing for a different thread, but I happen to love that combination.
I played trombone in hs/college, and it was great for my relative pitch and ear training, and consequently good for my ability to carry a tune as it lay in the human vocal range. And its parts were usually closely linked to the roots of any harmonies going on, but often in a songlike melodic fashion.
Bass is more, well, fundamental in its role, though it certainly can do many many things. If you can play the root and sing the third, then play the third and sing the root (inversion) or fifth, etc, you're getting on well with important basics of music theory.
And yes: study theory. It's dull until it clicks, then it's awesome.
