Use of royalty free/pre existing music in fan adventures: yay or nay?

Ive been thinking some concepts for my own fan adventures, and the one thing i always think about is "i cant compose SHIT", i have the art skills, a good narrative, the characters, interesting arcs, its just THE MUSIC.

obviousley some other adventures have used pre existing music once or twice, but like a full adventure with only borrowed music?

just saying in here if its a concern or theres nothing wrong with it