Kettle Drum Polka, written in E major, for some reason has sharps added next to the Ds. That is except for the four times that have a natural. So what gives?
It plays O.K. ignoring the added sharps.
At first I equated it to early written nuttiness, Buckley's Banjo Guide, but they went through the trouble to engrave new plates the same way in Dobson's New System etc.
Is there a music rule that I'm missing?