Just too many complaints and too many (and for too complicated) solutions are being offered. Here is my experience.
First and foremost, I am considered a windows phone '******' by those around me because I just the OS so very much on my mobile.
I really loved the default music and videos hub on 8.1. I never even thought of trying any other music player and often used to wonder why do others do so, if the native app is so good.
Then I upgraded to windows 10, got groove music as default and life began to take turn for the worse. Firstly, it did not recognize any songs and I was horrified if I have lost all my 1500 plus songs. Luckily that was not the case, just that groove could not 'scan'' those. True to my nature, I looked for possible solutions and I found one. It took nearly half a day (maybe the 640XL processor is slow for such tasks) to scan all but it did. However, it did not find my playlists. So I created a couple that I really need: one for my car and other of just rock songs. It went well for sometime, but then I received an 'update' for Groove. Then again, no songs. after trying a few things now I have about 16 songs out of close to 1600.
To make matters worse, groove does not support a Microsoft sign-in here in India. Most forums suggested I link it to my PC, have the groove app there and then try and resolve issue. but guess what? I DO NOT LISTEN TO SONGS ON MY LAPTOP. I firmly believe that MS totally forgot/ignored this fact while designing a player for mobile. They had something for the PC, which they transported to mobile space without sparing a thought on how people use it for the mobile. What is absolutely unimaginable is that they did it alright before groove. They simply killed something that had no issues and replaced with a crappy app like groove.
But I love windows, so am not switching platforms just for this. However, I love my music and that is probably the most used feature outside of calling and whats-app. So I tried a few third party music players. They are not great, but do the job. I am using Music+ right now. It surprised me by revealing the playlists I created in 8.1 and believed to have lost them for good. The only thing I don't like now on my mobile is that I am unable to uninstall groove music. I just don't to waste even a milli-second looking at it.