What's the exact difference between modulation, key change and tonicisation?

Question

I've always regarded a key change as the use of a completely different set of notes for the following music - definitely in a different key. Was in C, now is in C#, with no reason to suppose a return. Whereas a modulation is a more subtle move, perhaps to the parallel, or relative key (C>Cm, or C>Am) or the the IV or V (C>F, or C>G), where there's a lot of common ground between old and new, and indeed, there's a very good chance there'll be a return to the 'original key' at some point. The terms seem to be used interchangeably, so what's the truth of the matter?

Answer 1

Hi. You have a very good basic understanding of these concepts, although what you have stated isn't that far off there are a few details that you are missing. In most music a tonicisation is when a piece of music enters a new key only briefly, while a modulation is when music changes key long enough for there to be a cadence, such as a half cadence or a perfect authentic cadence. A modulation often happens with the intent of staying in the new key for a longer period of time or to not return to the original key at all. I hope this helps clear things up.