Someone sent me this question this week:
Why would a writer choose to modulate up a half step versus a whole step (or vice-versa)? Aside from the obvious answer that few would purposely modulate up to the obscure keys (F#Maj/GbMaj/BMaj), why would someone writing a song in the key of C modulate the final chorus to D flat versus D? Are there rules behind that?
He is correct in that most modulations of that type are half steps instead of whole steps. Curiously though, you won’t see people observe that rule when starting in F. They modulate to G rather than F#, because who wants to play in F#? (OK, I admit it; I do it too.)
Ideally of course, you learn to play in every key and I have actually grown a lot in that area over the last years. But I still have favorite keys just like everyone else and F# ain’t one of them;)
Let’s address a few questions here: why do that mod at all, and if so, is a half step or whole step better?
First, you most often do that mod for an energy lift. I can’t explain why it accomplishes that but it does, especially if you change up a few other things such as texture and tempo at the same time. If I do power ballads, I am going to use those mods. Often, I do more than one of them over the course of a song.
When accompanying singers, it is sort of a go to thing for the energy lift as well as a bit of variety. The half step is better than a whole step in those situations because singers have limited range. If you modulate a whole step, you are much more likely to put them in a key they are not entirely comfortable with. It depends on the song and the starting key.
When playing by yourself, whether your mod is half step, a whole step or some other interval is not really as important. Sometimes, the arrangement should drive it. For example, the chord progression of the song might have a natural modulation written into it.
As an example of what I mean, click here: http://youtu.be/X4Y4eWniH5o?t=4m17s This link will open “No More Night” starting at the last chorus. At 4:37, there is a smooth half step modulation. The reason it sounds so seamless is because I used the underlying chord progression to make it happen. There is a pivot chord opportunity written between the two keys. I won’t really go into that here, but if you are interested in learning more, check out this course.
Here is an important question though. Why do you need a modulation in the first place? I know that most piano arrangements have them, but in many cases, they don’t accomplish anything. IIf you don’t have a good reason to do one, don’t. Either the mod should be part of the story telling process or it is unnecessary.
About half of my arrangements use no mods at all. The ones that do usually use them to either change the mood or to build energy through a power ballad. Those may not be the only reasons to do mods but don’t fall into the trap of doing them because you think they are somehow required. They really aren’t.