For the gigging musician, go specialist (New Moon, Music Guard, Musician's Union, insure4music, etc.
If you're willing to take the chance or just jam now & again, then getting cover under your home insurance may give you ample cover, but often only covers in a vehicle if in a locked boot & out of sight.
I was covered with Blue Moon, but as I'm in the latter camp for the present, Home Insurance it is.