Growled vocals may have been a part of Viking music. In the 10th century, Arab-Spanish Sefardi Jewish merchant Abraham ben Jacob visited Denmark and commented on the local music as follows: "Never before I have heard uglier songs than those of the Vikings in Slesvig. The growling sound coming from their throats reminds me of dogs howling, only more untamed."[9]
In Hildegard of Bingen's 12th-century allegorical morality play Ordo Virtutum, the role of the Devil uniquely does not employ melodic singing, but is performed in a manner which Hildegard specifies as strepitus diaboli and which is often taken to mean a low and growling voice.[10][11]