wait, this game has Legendary Cards? Just kidding. I haven't had a Legendary drop yet, and I have opened, something like 200 packs.
Yes, instrument luck helps with music lesson skill points. I have focused on guitar, like a lot of people as it unlocks early, and you can craft guitars when you do the custom shop missions for parts. If you haven't done crafting yet, you should check it out.
Sounds like you are on Band Auditions. If so, that can be a bit of a grind. I got lucky and completed the band unlocks with 12 band audition runs. I hope that it goes at least as well for you as it did for me.
Rock On!
I think I need to level up a little more it unlocks at level 75 but I'm looking forward to the band auditions and then the next island!