one of the first things I made in order to sell was the Nintendetar guitar effect, this basically reshapes an input signal as PWM - it has proven reasonably successful though not successful enough to sell out of them!
anyway I have always been meaning to design a little add-on for it to make it more animated and finally I have done. Rather than redo the whole board and annoy everyone who bought the original I thought I would make a little stripboard add on daughter board so anyone that already has one can just add the board to their existing nintendetar effect.Here is a little song I did with the nintendetar to just show what it was good for Nintendetar Full song
the tricky part was getting rid of oscillator "ticks" which I managed with the aid of my resistor sub box (build one!) and getting the right rate range which turns out to be best between 0.3Hz and 4Hz ish - this particular oscillator is a Triangle one however you can also get some cool effects inputting different signals - a fast 10 - 20Hz squarewave for example give you a good stutter type effect