I've made a few additions to Prog:

Backgrounds

The visualise now provides a choice of 11 backgrounds. (OK, some of them are just horizontal reflections of others, but they give a quite different feel.

Smooth Spheres

A fifth kind of orbiting sphere has been added to the visualiser: smooth, non-metallic. Kind of like plastic or glazed ceramic.

Current Instruments

A popup provides a list of the current instruments while playing.

Endless and Loop modes

These automatically create a new section after playing the specified number of bars. Loop will just reuse the same parameters, endless will create a random variation similar to auto-section mode. You can also force loop mode to make an endless-style change next. There's an option for a queuing (or cuing?) a final section rather than just having an immediate stop, so capturing makes sens. Just don't leave it running too long, because capture is quite memory-hungry.

Bar Markers

And to help with embedding Prog in other projects (https://github.com/sarrowsmith/prog), it now unambiguously signals the downbeat of every bar.

Maybe I'll stop fiddling with it now and move on to something else.