I think we're agreed that definition questions like "What key is this song in?", "What instrument is this?", etc. are not good questions and will be closed shortly after they are posed. However, many new new/prospective users come to this site with exactly these questions.

It seems that this type of identification question is more commonly posed to/among musicians than to practitioners of other fields, so it is reasonable to expect that people will continue to ask these questions, no matter how many times we refer individuals to the tour page/chat and close such questions. 

It would save everyone time and probably encourage new users to ask better questions if we notified them BEFORE posting their question that it wasn't a good fit. It would help curious visitors to have a better first experience with the site than getting their first question closed, and it would save us closing questions - a win-win.

Some ways we could implement this:

1. A note in the "how to ask" box
2. A popup message like "Title must be at least 15 characters"

The popup seems likely to draw somewhat more attention, and should be pretty easy to implement. When you type the title, it already sends the title to the server for similar questions. Questions could be filtered for the "What...in" or "What...this" syntax and a warning returned. Alternatively, javascript can filter out such things right in the browser.