itch.io

I understand, you purchased / got permission from someone. But did they have permission to sell / give you the right to use that music? In  other words, probably not. 

The defense, "it was their "version" of the song" won't really save you should you go to court, for example. More than likely, they would also be held legally liable as well for profiting off of someone else's work. At best, you'd end up removing the music to avoid trouble anyway, and at worst they could argue that , because you're profiting from the game they are entitled to a percentage of your income.

Patreon / crowd funding is a bit of a gray area, since you're not "technically" selling the work - but I've known developers who have gotten in real legal trouble for less, if I'm honest. Princess Conquest comes to mind, they were immensely successful for years, until one day they were hit with tons of lawsuits. It took nearly a year and lots of money to sort out.

Anyway , ultimately it's your choice - I just thought I'd point it out. I'm a believer in informed decisions. Regardless of which path you choose, I'm sure the game will be great.