such was their joyful overindulgence , that when an ululation suddenly erupted , they all assumed it was one of them whod broken into shrill song , or that maybe it was the cry of the droll-looking beasts but then , raising his head and blinking his bleary eyes , yodren motioned them to hush and listened at the continuous , high-pitched cry , trying to make out the words and whether it was singing in jubilation or belligerence .