I am working (well, playing...) in ruby, attempting to create some useful audio tools. Not anything live, not something like a midi synthesizer or live action filters or an mp3 player. What I am making are simple tools that open a .wav file, modify it, and save it. I have good generators (square, sine, noise, triangular, sawtooth, etc... and more!). I have an envelope filter with which I am comfortable. I have a good tremolo (automatic envelope filter).
The closest thing I have to a low-pass, high-pass or parametric equalizer is a tremolo that runs into the audio range... basically turning the frequency up until the tremolo is in the audio frequency range. It's an interesting sound.
Do you know how to implement a parametric equalizer in ruby (preferably)?