Could someone help me in understanding how to access Pico-8 sounds programmatically? I'm very interested in building a little synth and sequencer but am unsure of where to start. Especially when it comes to editing the amp envelope (ADSR) through code.

Any help would be appreciated! Thanks :]

PICO-8's sound engine is quite expressive, but there's no ADSR envelope. If you haven't yet, it might be worth checking out Gruber's tutorial series for general perspective on PICO-8 sound design, plus the Music Editor section of the PICO-8 manual (especially the SFX instruments section), and, if you want to manipulate sfx with code, info on the sfx memory layout.

Another way to approach writing synths in PICO-8 is to build everything from scratch using the PCM output - here's a short article on how to set that up. It's limited to 5.5kHz but that's still enough to have some fun.

The sound engine in Pico-8 can achieve ADSR envelope-like effects to some extent in three ways.

1. Set the effects "slide", "fade in", and "fade out" to sfx notes (music01)　
2. Set the volume for multiple notes connected by the same pitch (music02)
3. Use a custom instrument to set the volume as in 2. and refer to it (music03)

1. has low resolution (but the volume changes smoothly), and 3. has high resolution.
In the end, you'll be using notes to create pseudo ADSR patterns.

[sfx]