Originally posted by Chris Fitzgerald
Oh, Jesus, THE PRESSURE... How do you guys expect me to perform under these conditions?
All I know about the practice of cancelling accidentals and showing a "courtesy natural" is that it's old school, and that nobody does it anymore. I don't recall seeing it in any 20th century music, but that doesn't mean that it doesn't exist. I also have it right here in front of me in Simandl, and I've also seen it in music that was roughly from that period (19th century) or earlier.
Whether or not anyone in the 20th century still does this, it's good to keep in mind that notation - like music - is an ever-evolving art form, and like anything else that grows, it sometimes has growing pains. For example, check on Finale for an option that will let you change key signatures with a full set of naturals from the previous key while adding new accidentals for the new key. This was common in older music, but gradually fewer and fewer people were doing it (they figured out that it was redundant), so now it's only an option on a software program. Things change, but it takes time. I guess that probably doesn't help much, but it's the best I can do.