I'm with Bruce - if you don't know/can't remember who wrote something and you picked up up from someone else's singing and playing, then that's folk. The works of Dibdin, Banjo Patterson, Sankey et al are now widely regarded as folk, and in the current generation some works by Ewan McColl, Lennon/McCartney have made it into the 'folk'canon. The fact is that someone, somewhere had to be the first to sing/arrange/play any piece, unless we subscribe to Aristolean concepts of spontaneous generation!