This is quite modern music notation. I expected something like neume notation, which I first saw painted on a mural inside a McDonalds, oddly enough.

Yeah. There is a whole academic and performance culture around historical music, and it's taught at music conservatoires and colleges. My wife for example plays and teaches music from the medieval, renaissance and baroque period extensively so I'm actually typing this in a room with shelves and shelves of facsimilies of scores from those periods all in original notation. With a bit of practise and training, people read this stuff just fine. From the Renaissance on there are lots of surviving treatises so we have a very good idea how they were performed etc and can in many cases be pretty confident that we're performing things pretty close to how they were done in the time.