I just got a new iPhone XR and realized that I have some music saved on my old iPhone 6s I would like on the new phone. The problem is the original mp3 files were saved on an old computer that I factory reset and sold years ago, and it is a very obscure band (I got the mp3s from a cassette tape converter and don't have access to the tape anymore). The band isn't on Spotify So the only copies of the files are on the iPhone 6s. My question is if there is a way to transfer music from one iPhone to another, or to move it from an iPhone to a Mac and then back to the new iPhone (I have moved local files from my Mac to my iPhone before, but not the other way around). The files are only stored in the Spotify app, not in iTunes or anywhere else. Sorry if this has been asked before - I looked and only saw questions about transferring from a computer to a phone.
iPhone XR/iPhone 6s
iOS 12/iOS 10