Myself and other higher level bards I know have all noticed the same thing.
Songs say percussion, but percussion has no effect.

Shada Silverleaf, Level 50 Bard, Mithaniel Marr
Erisi, Level 12 Paladin, Mithaniel Marr

<snip>

> > And I thought we had a couple high level songs which lowered
> > monster resists?
>
> At L46 our 3 magic resist lowering songs were resisted 100%
> of the time
> by the ice giants. To bring this a bit back to the theme of the list,
> has anyone else noted that even though the chant scrolls say they are
> percussion, playing a drum doesnt appear to make a darn bit of
> difference? I tested chant of flame and chant of ice on myself with my
> Mistmoore drum and playing a drum makes no difference either in the
> damage taken or the amount of resistance lowered.
>
>