Re: MP3 files play in QuickTime but not in Apple Music
they were imported from my previous iTunes library.
... the file opens and the song is played, but the sound is faint/fuzzy with lots of static
You may be playing the original file in QuickTime, and an imported copy in Apple Music.
Wondering whether the files were converted to a different format when you imported them into Apple Music. It may be worth experimenting with the format by importing one of the songs again, from the original file, taking care with the format choice. You can then test to hear whether or not there is a difference in the audio quality.
See Apple support's online article (link below) for all the know-how:
How to: Convert a song to a different file format with the Apple Music app
________
If needed: Music Support website: info. / support / contact options etc.
https://support.apple.com/music