My first sound box, I think I tried to put everything I had at the time (I was probably thinking about making a super full box and stopping afterwards, but that was just the start)
a old bike siren (with pitch hack), a saxophone toy for mini keyboard 1oct avec hack of the pitch too and a little tremolo, an old radio, old guitar pedal (dist, delay, whawha), and a passiv mixer
that with the recovery, a useless box now but it’s sentimental your 1st achievement that works
I posted elsewhere about the Science Fair “Electronic Organ” kit I built in high school. For my first actual synth, I built a PAiA Gnome a few years later.
Then I didn’t do much electronics for a couple decades. Got back into it with among other things an APC and a Weird Sound Generator.
I dug through a box in the basement and found that APC I made about ten years or so ago. Still works. I was amused to discover I used the same style knobs I use these days.