FreedymFry:Some, but not all, of the charms and mezes have a magic resist debuff built into them, making it easier to mez after they land or to reduce the chances of charm breaking early. The debuff is enhanced with an instrument. I believe they are all wind, but I guess I'd have to check. Better yet, go through the song list and look for A) debuff component B) instrument used.
This is close to being right, but not quite. The debuff you speak of on mez and charm is fixed and is not affected by the instrument mod. It neither affects the resist check adjust (present on the 70+ mez and charm songs) nor any debuff when the resist check passes.
I don't know if anyone has ever parsed mez and charm vs. instrument, but I've personally never noticed a difference in resist rate when using my best wind instrument vs. nothing. However, there is a huge difference when twisting in a song like HoS (or OoS).
It is true, though, that some song's debuffs are affected by instrument mods. Particularly the single target DoT and some of the AE slow/damage songs are affected by the drum or string instrument modifiers.
Check the spell spread sheet (I think the latest version is posted on The Concert Hall if not EQ Diva) that's available for all the gory details.