First, it's not a magical effect, but it's likely the closest out world had to magic. Music has been used to help teach catatonic people with neurological problems how to not just move again, but they can feed themselves breakfast! They do it in time to music! Or people with total memory loss that can still play whole Sonatas on piano!

So, you create a rote like a spell. It will have an area based on the volume of the instrument. You use Creative Writing + whatever lore is the subject the song to write the song. You will decide which "passion" the words are supposed to incite. On success you have a good song that can inspire passion! An Effect Bonus is a hit that raises the level of the passion. The beat of the song should match the passion. For example, if the passion is "Primal Surge", a passion that makes you faster, maybe it's a speed-metal song!

Now when played, the performer rolls Singing+Play Instrument (shared effort check) to determine the performance. Every listener then adds their own Aura check and if the song matches one of the listener's intimacies, they get inspiration on the Aura check. There may be passions like "Music Lover" that grants inspiration to this roll as well.

At lower results you only get minor morale bonuses. At a bit higher, you get that, plus whatever passion the song inspired. At the next tier, we add a temporary endurance point as well. After that, we increase the passion to a +2, etc.

So, different songs inspire different passions which may work with our intimacies and inspire different people more than others! The things you can inspire will depend on the songs you know, but you can always make something up and hope for the best!