The facts are that we have a corpus of songs collected from the tradition and which generally regarded as "folk songs", and that the overwhelming majority of them were at some point published on broadsides. There is also evidence from traditional singers themselves that they sourced songs from broadsides. This is not new to Roud, Lloyd made the same point. Are we to suppose that the songs the 'folk' took from broadsides were only those which had been taken from the tradition in the first place, and that they rejected everything else, including the most popular songs of their day? That seems unlikely to me.

The measure of whether a song is singable or not is whether it is sung. We are concerned only with those which were found in the singing tradition, so clearly these were singable. We can ignore that part of the output of the broadside presses which may have been unsingable.