Vocals

I must reiterate, we do not fully know what a Viking or Anglo-Saxon song would have sounded like, but we do know they made use of vocals in a musical context. The following sources are helpful in this respect: Tacitus in his Germania:

“They say that Hercules, too, once visited them; and when going into battle, they sing of him first of all heroes. They have also those songs of theirs, by the recital of this "baritus," as they call it, they rouse their courage, while from the note they augur the result of the approaching conflict. For, as their line shouts, they inspire or feel alarm. It is not so much an articulate sound, as a general cry of valor. They aim chiefly at a harsh note and a confused roar, putting their shields to their mouth, so that, by reverberation, it may swell into a fuller and deeper sound.”

This is highly suggestive of ‘throat singing’, and furthermore… Ibrahim Ibn Ahmad Al-Tartushi, upon visiting Hedeby around 950 noted:

“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.”

Adam of Bremen visited the temple at Uppsala, and wrote this (Gesta Hammaburgensis ecclesiae pontificum, IV:27):

“By the way, it is said that the songs sung during the ceremony are numerous and obscene, so that it is better to say nothing about them.”