With some diddling with Search on the Bodley Ballads website I've found that that 'Title, First line, tune keyword" means a single keyword from title, first line or tune, and the search doesn't work with more than one word entered.

I was wrong about no J. Pitts issue on the Bodley Ballads website. A Search on 'Black-bird' turns up addition copies printed by Catnach and Pitts with the note that the song is from 'The Tea Table Miscellany'. The Bodley Ballads website then (erroneously) attributes the song to Allan Ramsay.