I'm wondering if the Groove Music app for android plays music that you have stored on your device or if it only streams music.
According to the description in Google Play, it should play music offline if you upload your songs to OneDrive.
OneDrive
• Add your MP3s to OneDrive and play them wherever you go
• Download playlists, albums, and songs from OneDrive to enjoy your favorites even when you're off the grid
I just replaced my Lumia 950 with a Galaxy S7 and had all of my music on my 64gb sd card, but groove doesn't recognize it on the Galaxy. Play music does, but it still has me streaming music on groove music, which is what I really want to use. Any ideas?I tried that on my Samsung Galaxy A8. Then, I realized that I am using precious data whenever I play music during my travels. Decided, to load just 20GB of Music on my 64GB card and have peace of mind now.