Hi, Eoin -
In my opinion, most of the 305 Child Ballads were meant to be sung, not played on instruments. As I said above, Lesley Nelson's http://www.childballads.com/ has a generous selection of melodies on MIDI. Our threads crosslinked above tell the story of Professor Bronson and his 4-volume work titled The Traditional Tunes of the Child Ballads. Bronson has 146 versions just of Child #243 - but there are some ballads that have no melodies at all.

Loomis House Press has the four volumes of Bronson for sale at $40 apiece, or a one-volume condensation for $40.

So, my brief answer to your question is that I do not believe there is a collection of recordings of airs of the Child Ballads. There are extensive collections of sung versions, notably one by Peggy Seeger and Ewan MacColl; but not of instrumental versions.

That being said, our Digital Tradition Folk Song Database attempts to have at least one set of lyrics for each of the 305 ballads, and many have midi transcriptions of melodies. So, between us and Lesley Nelson, you have a reasonable selection.

-Joe-