Just for some information ... This is a period correct Blaupunkt with an aux in on the front which I play my phone tunes on... mine is standard but upgradable with bluespot amps...
(https://i.postimg.cc/RFqt4qX5/IMG-0140.jpg) (https://postimages.org/)
Some good info on period Stereos on here
https://www.bmwccgbforum.co.uk/ice-cool_topic8740.html