This from description in https://ddowiki.com/page/Item:Flametouched_Fiddle:
This fiddle is Bound to Account and has no race requirement (this has been confirmed by equipping the quiver on a heroic-level dwarf bard). On a non-scoundrel, it affects the way bard songs are played, however it does not play on every spell cast as it does on a scoundrel.
So how exactly it "affects the way bard songs are played"?