Free .PDF transcription of playing examples : http://www.AaronEdgarDrum.com/pdf/metricmod.pdf
What is metric modulation? Metric modulation, in a nutshell is when we either speed up or slow down in a way that’s relative to the original tempo/feel. The difference between an actual and an implied metric modulation is that in actual; we’re basing our pulse on the new tempo. So we really do speed up or slow down. (For example, in image number four at the bottom, the tempo changed from 150 bpm to 100 bpm). However, implied metric modulation is a trick or an illusion. We’re PRETENDING to speed up or slow down by basing our groove and feel on a different subdivision than we were using originally.
For implied metric modulation there’s a few ways we can go about phrasing these. (Not counting for the nearly infinite different modulations, I’m talking about musical placement).
- Forced resolve implied metric modulation : In a forced resolve implied metric modulation we would be placing our illusion into a number of bars that doesn’t fully fit the pattern. It’s like dividing two numbers that don’t work out evenly, it results in a remainder.
- Naturally resolving implied metric modulations : In a naturally resolving implied metric modulation we can creatively place our illusion within our phrasing so that it ends on beat one where we go back to the original feel. There’s a few ways to do this as well. We can make sure we use the correct number of bars to fill it up (for example three bars of 4/4 will fit a six quarter note long illusion twice). We can also take the same kind of illusion and place it starting on beat three in a bar of 4/4 so a bar and a half later it also ends on one. Finally, we can just change time signature to fit our illusion.
Implied metric modulations can be perceived as grooves and feels based on a polyrhythmic phrasing. In the above pictured examples the polyrhythm in question is four over three (cymbal versus actual pulse). We’re placing a groove into the spacing of that polyrhythm.
In actual metric modulation there are also a few different ways to perceive them.
- We can do a straight up tempo change although most of the time, numerically speaking these end up kind of ugly. Remember the dividing numbers with remainders reference? Same thing with your bpm.
- We can also perceive them as what Gavin Harrison calls a related tempo, which is a totally appropriate name for the real deal metric modulations. If you look at the implied examples above you see that the note rate for your groove went from an eighth note to three sixteenth notes. I’ll demonstrate that in the following picture as a real metric modulation. You’ll see at the bar line where it changes a dotted eighth note = eighth note. This signifies our modulation.
- Finally we can also take polyrhythmic phrasing like we spoke about above and use that as a basis to “pitch” our new tempo.
Of course we can go far beyond this. The examples shown here are specifically to get you understanding the basics. We don’t need to stay in the same time signature when we modulate either for real or implied. We don’t need to continue playing the same groove and it’s far more musical if we can disguise the transitions with fills.
I hope this clears it up for some of you! This is my interpretation of the topic. I know there are a lot of conflicting views on it, but this works for me and has done so for a number of my students. If you have any questions or still are having trouble understanding, please leave a comment! I’d love to help you out, but I can’t if I don’t know you’ve got an issue!
Keep hitting things