Hey,

I'm writing some music for Viola, What sort of intervals are easy to double stop on the Viola and keep in tune? Not including open notes which are obviously easy.

I've heard 5ths are hard, what about minor 3rds, Major 3rds, 4ths, flat 5ths, minor 6ths, Major 6ths, is there any simple rules I can go by?

Thankyou