If you are playing a non-bard character and use an instrument, if you roll a natural 20 on a performance check, your character shows a “natural infinity for music” and can play that instrument on a regular basis.
After 40 hrs of in-game practice, your character can play a simple tune with ease and gets advantage on performance any time they play that tune. Character must pick between: a rallying tune that makes other players feel encouraged (inspiring), a joyful tune that makes one want to dance (distracting/happy), a soulful tune (charming/alluring), or a lullaby (calming).
A player can choose to spend 40 hrs of in-game practicing per tune in order to learn all of them.
After mastering each tune, the character can play them whenever they are not in combat and have hands free to play the instrument. Each tune can add an advantage/disadvantage to those listening (including the player’s character, other characters, NPCs, etc.) within hearing range (60ft) for specific rolls depending on the tune:
Rallying: advantage on initiative (choose one character, including self) or athletics/acrobatics checks for all within hearing distance for the next 3 minutes (this includes any non-party entities)
Joyful: Works as an advantage on distraction, advantage on charm spells, or advantage on persuasion within the next 3 minutes.
Soulful: This gives advantage on charisma checks for the next 3 minutes.
Lullaby: This gives off a calming effect to all in hearing distance. This does not cast any spell nor make anyone fall asleep magically but it can ease tense, lessen arguments, and help others sleep better. If used during a short rest, it gives everyone within hearing range an additional 1d6 temporary hit points (cannot be replenished one spent) until used. If used during a long rest, characters need 1 hour less sleep and have an additional 1d12 hit points (cannot be replenished once spent) until used or until another long rest. D6/D12 rolled by person playing the instrument.