These songs are certainly evidence that the events took place - we have a number regarding undocumented information which, when asked about drew the response "I'd forgotten all about that", which led to more details emerging.
"but that will inevitably be coloured by their prior viewpoint."
Not too sure of this - the survival of many songs depends on their being accepted by the community.
It's true that some songs were deliberately composed to mislead; the bard who made The Haughs of Cromdale brought together two different battles to cover the ignominy of the Cromdale defeat
I'm left with the impression of the local songs we collected that they are basically accurate but sometimes over-creative in detail
Jim Carroll