Who are the Buddhist monks who chant/growl very low bass notes?

One night in 1433, the Tibetan lama Je Tzong Sherab Senge awoke from a startling dream. In it he had heard a voice unlike any voice that had ever sounded on the planet. It was a low voice, unbelievably deep, sounding more like the growl of a wild bull than anything human.

In this dream, Je Tzong Sherab Senge had been instructed to take this special voice and use it for a new chanting style that would embody both the masculine and feminine aspects of divine energy.

That year, more than 500 years ago, the Gyume Tantric Monastery began in Lhasa, Tibet. The monks of this monastery learned to chant in the same voice which Je Tzong Sherab Senge had heard in his dream.