Many of use that play bards have a love/hate relationship with them.
I have always enjoyed bards from pnp to other games. In most games people would take a bad bard over more classes(FFXI for example) Not that I am/ways a bad bard.
We all know bards have issues and underpowered, they are the least played class after druid(which can only be unlocked with VIP or TP). Bards need love, versatility and a unique play style. Instruments are the answer.
The idea: Bards start with "Voice" Perform instrument and get to choose a new one every 5 levels. Instrument are added to songs like meta-magic feats(pick which songs you want what instrument on)
Voice(Oratory/sing): Shortest cast time, shortest range can be used with fighting and casting penalty to concentration.
Physical(dance/act/comedy): Same as voice slightly higher cast time bonus to dodge line of sight(blocked by walls).
Percussion(drum/Cowbell?): Largest AOE long play time unable to preform other actions while playing
Wind(Bagpipes/panflute): Longer range on single target spells like Song of Capering unable to preform other actions while playing
String(Harp/lute): Middle ground in all
Second part of the idea equip-ables(named instruments and device) goes in off hand or quiver slot.
Sheet music:Exp song of Lost hope Inspire Courage gives +1 negative energy damage per 6 bard levels
Tuning fork: Playing any song has a change to cast random sonic spell
Metronome: Helps keep the pace going extends the duration of haste +3% double strike stacks with Inspire Recklessness
Make them have a minimum bard level to use and treat Perform instrument as a weapon type so if a bard doesn't have string and they equip on they get a penalty.