Non variant Music Packs are like regular music packs, that is, they’ll play through like albums or run in context mode but they do not contain mix variants such as “play with key up” “remove vocals”. I receive a lot of requests constantly for new music, to help provide additional new music to keep the game music ever fresh, this new feature has been added. So, non variant music packs are simply music packs without keyup, remove vocals mix variants. Play original and play music can be used and non variant packs can certainly be used within “play all music packs” and even “Play all variants” playback options, the pack will be included in these modes, but obviously will only ever play an original mix.
Non variant packs are added just like any other.