I just wanted to know about this but I learn stuff like everybody does.
I’ve done it two ways:
Simplest way is to record the game using the share function, then converting it to mp3 on the computer. Use an USB to get the video file from the PS4 to the PC. It’s the easiest way, but the sound quality isn’t that super good.
The other way is to get a capture card and record Dreams straight to the computer. This way you can get a high quality recording of your music. Only issue is that you need to buy the capture card, which can be a little expensive. I don’t have one myself, but I asked someone else for help.