Probably was. Super Furry Animals also had quite a bit of Welsh singing. My favorite band of all time, Manic Street Preachers, were from Wales but they did no native language singing that I know of. Apropos of nothing here. :D
Apparently there's some truth to the Aryan myth. Groups of horsemen galloping out of the Russian steppes, spreading their languages as well as other things...
I think Welsh is a language with little Indo-European influence. I just figure millennia of barbarians pouring in from the east should more than make up for such vast distances.
I figure that influences from the steppes of central Asia - both influences to European languages and Indian languages - took a long time to migrate from there to here, but that there was plenty of time to do so and the invaders from the east could be pretty insistent on forcing their ways on those they conquered.