Soon-A Little Night Music (I am auditioning for rapunzel in into the woods with this song and it took ages to find a backing track)
The only one that I've found is only on iTunes/Apple Music and it's from the album Sing the Songs of "A Little Night Music" (Karaoke) by Piper Tracks
I Know It's Today-Shrek The Musical (My sister is auditioning for little red in into the woods this one was a little easier to find
Waving Through A Window-Dear Evan Hansen (This one is without the backing vocals because my theatre camp friends and I were all singing a bunch of musical theatre songs and then then we had one guy sing the Evan part and the rest of us did the backing vocals)
Candy Store-Heathers The Musical
I found a candy store instrumental if you're one of those people that can sing all of the parts at once and I also found ones for each of the heathers if you are basic like me and can only sing one part at a time :(
Heather C:
Heather D:
Heather M:
I will update these when I find more! Feel free to put whatever backing tracks you find in the comments!