"Substantial Belches 21" is an audio recording that features exactly what the title suggests - a series of substantial belches. The audio takes listeners on a rather unrefined journey through an array of burps, each one varying in pitch, length, and intensity. The burps are undeniably gross, with each one sounding more guttural and gaseous than the last. The overall atmosphere created by the audio is one of amusement mixed with a certain level of discomfort, making it a strange but oddly captivating listening experience.