Bluetooth radio build.

There WERE cassette adaptors at one time, you pop it in and there is a input to the gizmo and you plug that into your phone etc

Holy crap that still exist
https://www.bestbuy.com/site/insign...tQxizGw4S5dtGrbJ_whPyatsDWRJu8KEaApaqEALw_wcB
Yep that's what i used to hook into my Walkman haha