I'm working on an iPhone app where I need to record audio, modify the audio to sound like a kazoo, and play it back. I don't need help with the coding aspect, but I do need help designing some sort of digital audio filter to produce a kazoo-like buzzing effect. I've tried ring modulators and reverb filters and nothing really seems to come close. I'm really in over my head and I could use any guidance anyone could give me.
I'm getting raw, linear PCM 32 bit floating point samples from the mic. After that, I can do pretty much anything to it. I was thinking of using some sort of low-pass filter to ignore higher-pitch sounds like "s" and then introducing some kind of noise.