I mean as soon as cassettes were a thing, mix tapes by holding the cassette to the radio became a thing right? Why not phones?

Hell back in the 80s, before the breakup of Yugoslavia, they went a step further: they had a home PC that could be built from parts available at electronics stores. It used a cassette recorder for a HDD.

A local radio station started broadcasting software, pc owners could record the audio of a program on a Walkman, then put the tape in their PC.

There's a past we never got where a radio-based internet existed alongside the landlines based one.