# Time Signature Change BPM Calculations?



## Default_M (Aug 30, 2009)

I have 2 riffs that I'm trying to record. One in 4/4 at 125bpm, and then I want to go in to the second riff which is 6/8.
I want it just to be a straight change in to the new one at the same speed, but just changing the time signature makes the 6/8 riff too fast.

I apparently need to program the BPM to change at that point as well to a much slower tempo in order for it to be the same speed as 4/4 at 125bpm.

Is there some kind of calculation to do in order to make sure I get the exact perfect tempo?


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## AySay (Aug 30, 2009)

what tempo is the 6/8 riff in?


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## Mr. Big Noodles (Aug 30, 2009)

This thread looks familiar.

Is the eighth note in 4/4 equivalent to the eighth note in 6/8? Have you considered making it 6/4? Having tempo changes between meter changes is usually not necessary.


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## Default_M (Aug 30, 2009)

AySay said:


> what tempo is the 6/8 riff in?



This is what I'm trying to figure out. In Pro Tools 90bpm feels like it is in the general ball park area but its not perfect and I want it to be a perfectly smooth transition.



SchecterWhore said:


> This thread looks familiar.
> 
> Is the eighth note in 4/4 equivalent to the eighth note in 6/8? Have you considered making it 6/4? Having tempo changes between meter changes is usually not necessary.



I tried 6/4 but it makes the riff sound way too slow if its still at 125bpm. This leads me to believe I may be trying to do what you said with the equivalent 8th notes?

I posted the thread on another forum too at the same time as I really want to try figure this out quick and get the song recorded today.

Someone asked me the same question on the other forum so I will copy paste what I wrote on there.

"I basically have 1 riff that I want to play in 6/8 then 4/4, so that it sounds the same speed but different notes are accented. Exact same notes both time, I just accent different parts so it has a different feel.
125bpm sounds right for the 4/4 part but I can't figure out the 6/8 part in Pro Tools.

Later I have a clean part in 4/4 at 125bpm and I want to go in to the 6/8 distorted riff and for it to feel like it was the same speed as the clean part before it.

Depending on the program I'm using; 6/8 at a specific tempo seems to be a different speed in each.
On my metronome 6/8 at 125bpm is very slow. Put it in Pro Tools and it's way too fast."


Basically, for it to sound the way I want it to I have to slow down the bpm of the 6/8 part, but I can't figure out the exact bpm that needs to be. At the minute I set it to 90bpm which is in the general area but not exactly perfect.


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## Mr. Big Noodles (Aug 30, 2009)

Maybe the metronome is counting the eighth note in 6/8 as an individual beat, and in Pro Tools, it's counting the dotted quarter note as the beat.

Do you want the quarter note in 4/4 to be equal in tempo to the dotted quarter note in 6/8? I'm not quite understanding what you want to do.


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## lnname (Aug 30, 2009)

here is( i am pretty sure) the exact answer you want: 

Do something called *temporal modulation*, (Metric modulation - Wikipedia, the free encyclopedia) you probabbly want to keep the same number of _bars _ per minute not the same number of _beats_ per minute.

4/4 at 125 quarter notes per minute equates to 31 and a quarter bars per minute. Translated into 6/8 that makes 187 and a half eighth notes per minute, or (94 and a quarter bpm on your software).

Honestly I would play your first riff at 124 bpm (125 isn't divisible by four so we get all those ugly fractions) then your second at 186 eigths per minute, which depending on your software might be written as *93 bpm*.

just to check that it is what you want, you can follow the link below to my bands myspace, our song ANNO DOMMINI uses this idea throughout. (self promotion!)


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## Default_M (Aug 30, 2009)

Thanks for that. Someone on the other forum told me to divide the bpm in 4/4 by 3 and then times it by 2 which equals 83bpm, so I'll be giving both a try shortly.


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## Teaboy (Aug 30, 2009)

Have you tried using triplets in 4/4?


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## TonalArchitect (Aug 30, 2009)

You could just keep the metronome at 125 and pretend like it's 3/4, but accent the notes as if it were 6/8, since they take up the same amount of time.


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## Default_M (Aug 30, 2009)

Its too late for me to pick up my guitar now because of the noise, but I'm not sure if I understand what you mean?
A bar of 6/8 has 2 beats while 3/4 has 3. Surely it would change the feel?


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## Seedawakener (Aug 30, 2009)

ok... There are two ways to do it. I don't quite understand the problem though. Either you want both of the meters to be the same length, in that case: Use the same time signature (4/4) and use triplets. If you want the signature to be 6/8 (which is just as long as 3/4) it will sound like 6/8. Changing tempo seems like overkill if you want a smooth transition. The only time you'd need that is when the riff can't be played like triplets or in 6/8.


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## Mr. Big Noodles (Aug 30, 2009)

Seedawakener said:


> ok... There are two ways to do it. I don't quite understand the problem though. Either you want both of the meters to be the same length, in that case: Use the same time signature (4/4) and use triplets. If you want the signature to be 6/8 (which is just as long as 3/4) it will sound like 6/8. Changing tempo seems like overkill if you want a smooth transition. The only time you'd need that is when the riff can't be played like triplets or in 6/8.





Also, here is what is meant by pretending a bar of 3/4 is 6/8.
Eighth note = 
Accented eighth note = >

3/4 looks like this:
>>>

6/8 looks like this:
>>

Both have six eighth notes in them, but the accenting pattern is different. A common syncopation in simple meter is to briefly suppose that it is a compound meter, which is to say that a piece in 3/4 can have measures that sound like 6/8, but you don't have to change the written time signature. Writing your 6/8 riff as 3/4 is a bit unnecessary for your purposes, though.

What we're getting at is to make the value of the eighth note in 4/4 the same as the value of the eighth note in 6/8.
>>>>>>

If that is too fast, you can make the value of the quarter note in 4/4 equivalent to the value of the quarter note in 6/4.


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