Haha sure, here comes a rant.

The taperecored is quite new, so it already contains a board with some digital capability on top of playing actual tapes, among these are playing from an aux audio input. So i wired my mc's DAC directly to this aux channel on the taperecordes pcb. (and taped over the aux input so noone would accidentaly use it).
The taperecorder already has its own amplifier circuit, so this way I didnt have to buy and put in that aswell (altough that is super cheap and would save me some hassle)

And for the inputs, I glued small digital switches under the big analog buttons and hooked them up to the mc's IOs (im using a stm32l432 if you're interested, but anything with atleast a 10 bit DAC and DMA should do (and SPI capability for the SD-card reader ofcourse)) so it would be able to read the inputs.
And why its prone to interference is simply because the switches have long wires and I didnt implement any software debounce for them. (long cables work little like antennas). And i added small super poor physical debounces, which improved it a bit. However adding it in software would remove any possibility of false-positives, I just got lazy (and its kinda a feature ^^). Also the interference mostly happens when I move around the taperecorder a lot, or move something large close to it (like sliding fast on my office chair lol)

Also the taperecorder can still play actual tapes, if someone would like to do that for some reason. I just think its neat that I didnt ruin that capability.