Ok. So i am showing gloves only have Percussion Resonance 26 (Free to play bard) and MM Battle Drums have Percussion Resonance 35
It depends on the rank of your songs, since bard focus has never been a good design. Free to Play means either rank 1 or 2, if you bought the unlock. You are limited as a result. This means if you're using rank 1/2 songs, the higher focus does nothing, since you're over the rank 1 cap for song focus, think rank 2 is 34 cap. It also depends a bit on AA and level, since those are how you hit those caps and I forget when that occurs, but it was pre-85 somewhere.
Also, note that those +25% melee instruments were always less DPS than dual-wielding and using the armor focus instead. The +1 tick on the mez was just about the only reason to use them, or the minor boost to selos for those that cared, which put you barely over the speed of the fastest horses. This only worked with the songs though, not the AA.
Found the equation for figuring it out :
This works together like so -
1.0 (Base Song Mod) + 0.8 (Instrument Mastery 4) + 2.6 (____ Resonance 26) = 4.4 = 440% of base
caps are 32/34/36 for ranks I/II/III ... so you're hitting the cap with your gloves either way. Yes, bard focus is stupid.