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Pitch to tempo mathematics...

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Pitch to tempo mathematics...

Postby siderealxxx » Mon Dec 17, 2018 1:35 pm

Hi, interesting conundrum here...

I wish to record a vocal at one (lower) pitch and play it back at another (higher) pitch with a predefined tempo (120bpm) in order to get that old-school pitched rave vocal effect (i.e. the song is at 120bpm so I want to pitch the vocals up to match it).

So Melodyne etc is out the window because that's just pitch shifting, and using some other formant based process gives different results (unless I'm wrong?). I simply want the sped up effect you'd get by mapping it and playing it across a sampler.

So my question is, what is the formula for calculating pitch to tempo? Let's say I wanted the target vocal in Fm at 120bpm, and I recorded it 5 semitones down in Cm... what tempo should I record the original vocal at so it will align at 120bpm?

I'm not so good at maths so need help thinking about this. And I'm looking for a formula not the answer, as I don't know what will work best yet.

Hope that's clear...! Thanks
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Re: Pitch to tempo mathematics...

Postby Wonks » Mon Dec 17, 2018 2:11 pm

You've almost answered your own question as you've already made a note frequency chart.

So read off the frequency of an original note, divide that into the frequency of the slowed down (or sped up note if going the other way), then multiply the original tempo by that value.

For speeding up, lets say A4 at 440Hz and 120 BPM. Five semitones up is D5 at 587.33Hz. 587.33/440 = 1.335 (to 3 decimal places) . So 120 x 1.335 = 160.2BPM

And for slowing down 5 semitones down it would be the other way, so 587.33/440 = 0.749. So 120 x 0.749 = 89.88BPM.

But you really need top use more decimal places if possible to get a more accurate and consistent shift.
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Re: Pitch to tempo mathematics...

Postby siderealxxx » Mon Dec 17, 2018 2:17 pm

Wonks wrote:You've almost answered your own question as you've already made a note frequency chart.

So read off the frequency of an original note, divide that into the frequency of the slowed down (or sped up note if going the other way), then multiply the original tempo by that value.

For speeding up, lets say A4 at 440Hz and 120 BPM. Five semitones up is D5 at 587.33Hz. 587.33/440 = 1.335 (to 3 decimal places) . So 120 x 1.335 = 160.2BPM

And for slowing down 5 semitones down it would be the other way, so 587.33/440 = 0.749. So 120 x 0.749 = 89.88BPM.

But you really need top use more decimal places if possible to get a more accurate and consistent shift.

Ok thanks! You make it sound so simple, don't think I would have ever worked that out :)

Will put it to the test! Cheers
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Re: Pitch to tempo mathematics...

Postby Sam Spoons » Mon Dec 17, 2018 2:17 pm

Reaper or Melodyne will time stretch/contract without pitch change or change pitch without time stretching a track so you could make a best guess and tweak it later.

But a 5th down would be 2/3 the frequency of the target key so record at 80BPM and you should be very close (then autotune maybe)?

I won't work out the formula as Wonks has done that. :clap: :thumbup: :D

edit :- just realised you said 5 semitones not a fifth.......
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Re: Pitch to tempo mathematics...

Postby ManFromGlass » Mon Dec 17, 2018 2:30 pm

I’m crap at math so being a logic user I would just use Logic’s sampler plus pitchbend for fine tuning. Unless I’m missing the point, which is very possible.
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