Any ableton users out there? Check out my Max4Live device: PoopBox. It is a digital emulation of the legendary Blippoo Box by Rob Hordijk. I tried as best as I can to replicate every detail and add some of my own features. It is perfect if you need to design some gastric sounds.
The Blippoo box features two oscillators that modulate each-other, which are then fed into a digital shift register and sample and hold. The results can be sent back to the oscillators, or to a special Hordijk filter called the Twin Peak filter. This filter features two lowpass filters but with one of them phase inverted. This combination creates a bandpass with two peaks on each side. This filter can be further modulated by the sample and hold or shift register.