C Forde built an MP3 player shaped like a cassette tape, and posted the build on Hackster.io. It plays through headphones on its own, or it sits in a cassette deck and feeds audio to the player’s own head through a tape head mounted in the shell.

Version 2 replaces most of the point to point wiring with a 2 layer flexible PCB. The cassette shell is 3D printed in four pieces with cutouts already in place for the USB socket, MicroSD slot and headphone jack, so there is no need to cut up a real cassette. The spools are printed too, and they turn.

Inside is an ESP32-C3 mini with an integrated OLED display, running MicroPython, driving a DFPlayer Mini. A 150mAh LiPo powers it, with a resistor divider on GPIO2 reporting charge as a percentage on the display. Five tactile buttons under a printed front panel handle play, stop, volume and track skip. A switch behind the tape head starts playback when the deck’s mechanical play button presses in. Running current is about 50mA.

See more at hackster.io.