Is it possible to make a "Sony CFS-201" cassette player/radio output sound from an external source?
It may be possible to hack into the audio amplifier by feeding your signal into the "top" tag of the volume control as this is a common point between the pre-amplifier and the "power" amplifier.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Tapping into the volume control.



Figure 2. A cassette adapter. Source: Wikipedia.

Another - no-hack - option is to use a cassette tape adapter. These are basically a cassette with a play head mounted to face the play head in your player. Your plug the device into your modern player. You can make one and should be able to find plans on the web.