Making triplet equal eighth note in metric modulation?

• Jun 18, 2021 - 00:04

Hey everyone, I'm developing a Drumline exercise that begins in 4/4 with duple rhythms for 2 measures. In the final beat of the second measure, I have a triplet that I would like to be the same rhythm as the ensuing 12/8, which is the base for most of the exercise. so, the eighth note needs to equal the triplet speed. Any ideas? Thanks in advance.


In reply to by jeetee

And then do the math :-)

First thing to know is that MuseScore always consider quarter notes to be the definition of beat as in BPM, so in your 12/8 bars you have six beats per measure. (but we all know that you actually have 4 beats, but for BPM calculation you need to think about it as six beats.

if you have x BPM in the 12/8 part, that means that you have

x * 2 8th per minute, or 1/(x*2) minutes per eight-note

if y is the tempo in the 4/4 bars, then you have

y * 3 triplet-eigthts per minute. or 1/(y*3) minutes per tripplet eight-note.

Now you want the triplet eighth-notes in 4/4 to have the same length as the eighth-notes in 12/4. That means that you say that
1/(x2) = 1/(y3)
Which means that
x = y * 3/2
y = x * 2/3

So if you what the BPM of the 4/4 part (y) to be 100, the BPM on the 12/8 part should be 100 * 3/2 = 150 BPM

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