Wow just looking at your FX processor, that's a proper project, and you even include some math, nice! I very well may make a version. My FX processor is a ZOOM9000. Sometimes even when it has power, it won't turn on, but I never found a power issue. Someday, I'll have to start probing the IC's.
Compared to the few AVR projects I've done from scratch, I really don't know how much more complex something like an FX pro. must be, or how fast it would have to be for audio and everything else to be done.
1 of the 1st digital audio things I want to make is a timer for my stove, and I'll make it with the piezo from a microwave. I suppose I could mod my microwave, but I don't want to take that apart.