Our instructions for the marking task say something like 'Draw rectangles around the titles of plays featured in the next performance' because we're interested in the works performed, but what counts as a 'performance' of a work?
Plays do, of course, but what about other things? So far I've noticed 'musical interludes', 'excerpts' (sometimes with the specific act listed), 'amusements', 'burlettas' (brief comic operas), lectures and 'addresses', and even acts by dogs!
We aren't expecting songs to be included, as they're generally listed as part of a larger performance. Animals tend to be listed with their name rather than the title of a work, but that may change as we work on other playbills from other places and periods.
Our rule of thumb for now is 'if you're not sure, include it and we'll work it out later'. We're consulting with academic historians, but we'd also like to hear from you. Have you come across types of performances that you weren't sure about? What information would researchers want to search on?