There are lot's of musicians gathering at Steemit Open Mic (the longest running music community on the platform) which I host and you can find on my blog, but there are also other musical communities that have spawned from there.
Try these tags looking at both the new and trending tabs of each tag.
There is a beatbox tag but it looks like someone started it and dropped the ball. Maybe you can revive it yourself.
I really want to revive it Sir but I don't have enough SP and SBD to make it possible maybe someone will help me to fund it for the goodness of the community I can really revive it and I can campaign many beatboxers here in Ph and most of all to the whole world :)