In reply to Alex Pryor:
Yes I did exactly this on the one car I’ve ever owned that had a USB socket, it was perfect (it didn’t have Bluetooth so I couldn’t do it via the phone and as you say, it doesn’t tie up the phone or whatever)
Now I don’t even have Aux input as my car is old. Got a 6 disc player and a tape deck though ha ha
actually many many years ago, before USB was common, I had a Discman thing that could play CDs full of mp3s and I would use this in car via one of those fake cassettes with a wire (poor man’s “Aux in”), worked quite well actually