I can't help but I have this in my head in the last few days:

-Yona as a drummer
-Sandbar and Gallus as badféank bass guitarists
- Ocellus playing on sax
-Silverstream and Smolder are singers of the band.

7154145
Well, Silverstream was shown to be playing the saxophone in A Horse Shoe-In...

Personally, I always figured Smolder to be the drummer type. A dragon basically just banging on things all the time with nobody complaining--what's not to like about that?

7154165
Yeah, now I remember how spike was drumming on two shells at the end of the movie, yet Sandbar and Gallus could play on a bass guitar, especially Gallus with his fingers.

I've had a lot of time to think of this.

I've generally gone with

Sandbar -Lead Singer
Ocellus - Back up singer and Lead Guitar (mostly just because bass is too perfect for Gallus)
Gallus -bass guitar
Silverstream - Sax
Yona - Drums
Smolder - Keyboard

The last one just because I'm a fan of the idea of Spike teaching Smolder to play paino