G'day Bob,
hmmm. Is a drummer a musician? (I regularly tease my son about giving up music to play the drums )

What about other percussion? Is a percussionist still a musician if (s)he decides to experiment with other objects to hit?

I would say: "Of course they are.".

OK, what about a didgeridoo? Strictly speaking a didge. is a brass instrument (played by buzzing ones lips in a mouthpiece) but you also sing into a didge. As well as glottal stops and other vocal techniques... Is this singing or playing?

What if I use a megaphone? Like a didge. it will amplify my voice - am I still singing or am I now playing an instrument?

I guess we have a somewhat different perspective. I'm a brass player. We brass players are intimately connected to our instruments using all the vocal apparatus of our bodies (including the vocal chords for some effects) in a way that no other instrument is. We-ell OK, other wind instruments do come pretty close...

OTOH you are a string player. No part of your vocal apparatus is involved in playing your instrument. (unless, like me, you need to "hold your mouth right" when you're concentrating )

I guess point of view is really important.

--=-- My credo: If it's worth doing, it's worth overdoing - just ask my missus, she'll tell ya laugh --=--
You're only paranoid if you're wrong!