Don't know if this has always been available and I'm just now discovering it for myself, but if you search for something in Groove Music (artist, album, song, etc.), there's an option at the top of the list to search through "full catalogue". Doing so will give you results from all of Groove music and let you play full songs and add to your collection if you have a Music Pass. Again, this may be old info, but I haven't heard anything about it, and know that the inability to take advantage of Music Pass was keeping several people from trying W10M.
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