[ItsMikeE]

Following the update to Android M I did a factory reset and set up adoptable storage
Then I downloaded all my music to a folder on the phone

I was able to tell PowerAmp where the music is and that works fine, but both Google Play Music and HTC Music cannot find any of my music.
This did not happen on Android L when I had all my music on the SD card

Is there a way to tell either Android or the two music apps where my music is?
Or do I need to move my music to a standard location?

[ItsMikeE]

Found the answer myself

Go to Settings, Apps, Show System
Choose Media Storage
Then Storage and clear data

Restart phone and media database is rebuilt

[LeoRex]

Yeah, mediaserver doesn't automatically reindex media files when they are moved in by hand. I know that if I copy in files from a computer to be used for things like notifications and ringtones, I usually reboot the phone to make sure. There might be an app that you can trigger the index manually, but a reboot works just fine.