| Kevin Andrew Murphy Contributor |
I'd look at the old "Instruments of the Bards" from Complete Arcane from 3.5. I believe they're all product identity/non-OGL, but will still work in a Pathfinder campaign due to backwards compatibility and will give you an idea on how to make such an item as you want, or more to the point, price it. Glancing over them all, all I see is bonuses to Perform and a bonus ranging from +1 to +7 for bardic magical musical abilities but not actual spellcasting.