Thank you for the very generous reply and suggestion. I'm kind of a noob at this and not really understanding what sideloading a music app is. I did a quick google search to no avail. Please note, my CD collection is ripped to FLAC if that matters in what app I should try.
No worries. Refer to what 'superuser1' said in post #3388, that's exactly what sideloading is. Pretty easy. And your audio files can be in various formats, be it FLAC or MP3, etc, and you can still use almost any music player app to play it on the M6.