Do you have any suggestions for creating time-based effects (delay, reverb, etc.)

[beatsbears]

I'm very interested how these types of effects could be supported using the libraries available today, or whether there need to be some fundamental enhancements made to audiomixer or something downstream of synthio.

[todbot]

This is something I would very much like too. Unfortunately, there is no audio processing capability in CircuitPython and afaik, no plans for it. But you are correct, the place to start would be AudioMixer, as it's the only object that even has the concept of an in-to-out audiostream.