At least the oldest cars had a cassette player, so you could use a jack cassette adapter[1] and listen to music on your phone/mp3 player. The more recent one would have mp3 CD players so you could burn discs with hundred of hours of music. But the worst are the car in-between, with no Cassette player, but only a CD player, where you could burn at most ~20 tracks on those 650MB CD-R.

[1] https://www.amazon.com/Insten-Cassette-Adapter-Compatible-Pl...