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.

https://maxforlive.com/library/device.php?id=7489#17644

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.