And now for a feature request: LFO control the mix.

I'm starting to find that my mix is noticeably repetitive after a few minutes. I would like the app to automatically bring in and out other selected sounds over a period of time to reduce the repetition.

However, I know this flies in the face of simplicity, I don't know how you'd go about adding that in a way that's easy to use? Perhaps you add some "timers" and link them to sounds, such that each "timer" fades in/out over some preset periods (1/5/10/15 minutes ?)