iPhone XR Transferring music from NAS to iPhone XR

[JoeSchmoe18]

My Apple Music keeps pointing to my MBP and I have 100GB of music on my NAS. I want to be able to manage my music manually from my NAS and be able to load it onto my iPhone XR.

What is the best way to use my music on my NAS and move it back and forth to my iPhone XR?

Fighting with the lame Apple Music is just to much time to make it work right, are there free apps that can do this? Can I do it through Finder some how??

 

[Minorite]

You can transfer them to iTunes, sync, then delete, but not sure it's what you're looking for. iMazing can do what you need, but it's paid. On sale here for $20 if you'll decide to buy it.