In NZ, I have the instruments noted on the house insurance. Valued by a registered instrument valuer, photographed, and the documentation lodged with the house contents insurance. Also the stereo, LPs and tapes (worth nothing) and the CDs (worth little).
I really should have my tools valued, because between them, tools and music are worth much not much less than our furniture and clothes and chattels.
Worth more, to me.

TELL your insurance company. They will certainly not hold insured portables that they don't know about. And they only pay out second-hand value anyway.