[kiloDalton]

In the case of lossless files, the takeout files are empathically not the same files that were uploaded. Google Music would allow a user to upload lossless FLAC files, but internally it converted them to 320 kpbs MP3 files. So, GPM certainly transcoded a portion of uploaded files. I'm not sure to what extent it left files alone if they met Google's formatting specifications. Perhaps someone else knows.

[jeffbee]

I don't think they did very much leaving things alone. One of my biggest problems with GPM was that my uploads would seemingly get de-duplicated alongside some other record that wasn't exactly the same, like a reissue or a remaster of the same record that sounded noticeably different. Sometimes an album I uploaded would gain a mysterious bonus track. They also at some point hosed up the whole system in such a way that many of my records contained every track twice, which meant I had to make playlists out of my old albums just to remove the even-numbered tracks and make it listenable again.

If you takeout from YTM it says your music files are "Your originally uploaded audio file" which is nice. Since music in YTM may have been migrated from GPM, that seems to imply that GPM retained the originals.

When they shut down GPM I migrated to YTM, which doesn't seem to have these specific catalog problems. I also just re-organized my local copy of my FLACs using MusicBrainz Picard. Unlike this author I no longer have the giant wall of CDs!