Defender Sound Studio
Link: https://www.zapspace.net/defender_sound/
Discussion: https://news.ycombinator.com/item?id=41911575
Re last boosted link, this allows you to play with the audio generation code of the Defender arcade game which, if you read the help page was way ahead of the time. Might as well also throw in this page, which is a similar concept but for the generation of Pokemon cries in gen 1 which also worked in a really interesting way. There's a video to go with this one that goes into more detail linked on the page https://ardean.github.io/pokemon-gen1-cry-synthesizer/