"And the bard is picked out by his Agwen, not only to delight his lord, but to remember all the great deeds and great men in his clan, all in their proper order. For if men were without knowledge of anything but the name of each man's father, then the children of bondsmen would be as noble or base as the children of a gwerbret. Therefore, let no man or woman either commit the impiety of raising his hand against a bard."
The bards' role in Deverry is a very important one, as can be seen by the above quote. They were there to understand the geneologies of each clan, so the Lord or King did not have to worry about who was his cousin, dead these many years, or even when it was his relatives birthdays! As well as to entertain the hall.
However, the bards also played a mystical role, as they accessed all this information via their agwen, or trance. The trance state led them to another world, where they confronted a personification of the agwen. For some it was a woman, others just heard a voice. In it's own way it is the equivalent of a dweomer master entering a trance state to reach the aethyr. Which is why some bards throughout the Deverry series tend to have the Wildfolk flocking about them continually. The other reason being that Wildfolk do like good music as well!