quick tutorial for calculating bpm's / matching bpm's

baggysound

baggysound

Radioactive
so, i decided to write a short tutorial for my fellow future producers..

this time i want to answer the ever so often asked question "how do i find the bpm's of a sample and then adjust it?"


ok, first of all (thanks to Bruce Leroy for pointing to this link in a different thread) you should download this tool for finding the correct bpm of a song/sample

http://www.analogx.com/contents/download/audio/taptempo.htm

(sorry, this software is for windows user only)

for getting the correct setting you simply start the program, play the desired song and press the spacebar on every beat and after a few seconds you will see the tempo in the display

when doing this you have to be careful that you really hit the spacebar correctly in sync with the beat, otherwise you will get wrong results..


next, if you haven't done this already, you can use your favorite audio editing tool to do whatever you want to do with this sample i.e. loop it, add effects or change the pitch.. (in my case adobe audition)


ok, so far so good, but what if you have two samples, but they play at different bpm's and you want to match them?
or what if you want to change the tempo of one sample to a certain desired tempo?


some audio editing tools, so i have read, allow you to enter the current bpm and change tempo
to a special bpm-setting, but those, to be honest, i have never worked with, so i tell you "my way"

i have worked with adobe audition where you can only change tempo to a certain ratio and here a simple calculation helps out:



*going back to maths class*

  • we have the tempo "t"
  • we have a desired tempo "dt"
  • and we have the needed calculation factor "f"

the general equation looks like this:

t * f = td so f = td/t

let's imagine we have a sample playing at 64 bpm but we want it to play at 96 bpm, then our equation would be:

64 * f = 96

to get "f" we simly divide "dt" by "t", in our case 96 divided by 64..

the result in our case is 1,5.. i chose these bpms on purpose so we receive an easy factor to calculate with. this will not always be the case, but don't be intimidated if you get a result like "1,340503024304923", you can just round the result to approx. 5 digits and should be close enough ;)

by the way, you will always receive a number higher than 1 if you want to make your bpms faster, and you will always receive a number lower than 1 when making the samples tempo slower


within adobe audition/cool edit pro you have to enter a certain ratio for changing tempo. this ratio is compared to "100 f" whereas the result of our calculation is only "1 f". so we simly multiply our result by 100, in our case 1,5 * 100 making the proper number to put into the ratio field "150"

if your "f" turns out to be "1,340503024304923", then "134,050" should be close enough


now you have your sample playing at the desired tempo and you can fully integrate it in your track

happy producing ;)
 
What the hell was that complicated math stuff about. There is a much easier way to find the bpm of a sample without using a therum. All you have to do is put the metronome on while you play the sample. Which ever tempo you speed it up to or slow it down to when it becomes in sync with the metronome click is the correct bpm.

Simplified:

Sample + Click + Speed up
or Slowed down tempo =
correct calculation of
bpm.


Or you can use the time stretch feature.
 
that might work but if you do it baggys way- yes, math- you can get your samples and accapellas to match up really really well. i do it with a calculator and soundforge, and try to get like two or three decimals, and you can get a whole verse of an accapella to line up perfectly. no fudgin with it or choppin it up....

but i guess you only really need that if you have big long samples to stretch.... i dunno. it pays to be precise.


peace.
 
A-L Productions said:
What the hell was that complicated math stuff about. There is a much easier way to find the bpm of a sample without using a therum. All you have to do is put the metronome on while you play the sample. Which ever tempo you speed it up to or slow it down to when it becomes in sync with the metronome click is the correct bpm.

Simplified:

Sample + Click + Speed up
or Slowed down tempo =
correct calculation of
bpm.


Or you can use the time stretch feature.
Click to expand...



ok, let's imagine you have 4 samples playing in a different speed and you want to match all of them to a certain bpm.. i bet using my calculation you're much faster to get the exact result than having to "try around"


and sorry, if "b divided by a" is a difficult calculation for you, then you should get back to school for some basic maths courses
 
Thanks man, I was kind of curious how BPM changing was done, that kind of helps a little bit and definately the fact you use Adobe Audition helps because thats what I am trying to get a grasp of and that little tutorial helped me work out several more things than you may realise. Peace.
 
hi sean,
first of all welcome to fp :)

i'm glad this tut was helpful to you.

if you have any questions just go ahead and ask them (but please use the search function in advance)
 
If you're using Audition, all you need to do is chop the sample so it has the exact amount of beats, say like a 1 bar sample has 4 beats. Then just go to the View menu, Wave Properties, Loop info tab, then enter the beats and it will automatically do the math for you and tell you the bpm. Choose your stretch method (time scale stretch or beat slice) then save that into the file. All the properties are set and you can use that sample/loop into most popular apps, Audition, Acid, ProTools, Sonar, Cubase, etc and it will automatically do all the stretching to fit the bar for you. No math needed.
 
dtwizzle said:
If you're using Audition, all you need to do is chop the sample so it has the exact amount of beats, say like a 1 bar sample has 4 beats. Then just go to the View menu, Wave Properties, Loop info tab, then enter the beats and it will automatically do the math for you and tell you the bpm. Choose your stretch method (time scale stretch or beat slice) then save that into the file. All the properties are set and you can use that sample/loop into most popular apps, Audition, Acid, ProTools, Sonar, Cubase, etc and it will automatically do all the stretching to fit the bar for you. No math needed.
Click to expand...


i still don't see how this should work with multiple samples at different speeds to make them fit

the math is only if you want to match different samples to the same bpm

eventually it would be good to read the whole post and not skip parts of it
 
This does work with multiple samples at different speeds. I'm not saying your way of doing it is wrong, I'm just showing a different way to do it without using a calculator. If the bpm and the number of beats in the loop/sample is embedded in the file, then most popular software will read that information and automatically calculate how the sample needs to be time stretched or time compressed to fit. I use this my method with acid and sonar all the time and i've never used a calculator.
 
oh, ok thanks for adding this then..

i have never worked with acid or sonar, so i can't tell

the automatic bpm calculation within adobe audition has hardly ever worked correctly for me, so i rather do it this way, to make sure it's really exactly how i want it to work.

this calculation works the same for my harddware sampler as well..

thanks for adding your way of doing this btw ;)
 
Props on the tut BaggySound. I am trying to see how I could apply this theory to SoundForge. In time stretch, it has a slider bar and shows you the percentage of the original source, but I dont think this same method works. Any suggestions Baggy?
 
kontak80 said:
Props on the tut BaggySound. I am trying to see how I could apply this theory to SoundForge. In time stretch, it has a slider bar and shows you the percentage of the original source, but I dont think this same method works. Any suggestions Baggy?
Click to expand...

you can change the read out to percent, or bpm, or....TIME. thats the way to do it.



peace.
 
kontak80 said:
Props on the tut BaggySound. I am trying to see how I could apply this theory to SoundForge. In time stretch, it has a slider bar and shows you the percentage of the original source, but I dont think this same method works. Any suggestions Baggy?
Click to expand...

thanks kontak

to change in percentage? well, let me calculate a little if my thoughts are right

to how many digits is the percentage change possible? 3? 4? (so i.e. change by 91.133% to make it slower)

or could you post/send me a screenshot of that bar?

edit: never mind that screenshot, the calculation is in the next post
 
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here's the calculation

when making a sample faster:

you divide the desired tempo by the given tempo (i.e. 96/64) but then you subtract "1" off this result and then multiply by 100

((96/64)-1)*100 = 50

this result (50) would mean 50% so you'd have to make the 64bpm sample faster by 50%

if you have a 33 bpm sample but want a 99 bpm sample (99/33 = 3.. 3 - 1 = 2 .. 2 x 100 = 200%)

to check this equation you can caluculate with the same bpm

i.e. 64/64 = 1
1 - 1 = 0; 0 * 100 = 0% so you would have to change a 64bmp sample by 0% to achieve a 64bpm sample


when making a sample slower:

you calculate (1 - (desired bpm/actual bpm)) * 100

to check this calculation:

actual bpm: 96
desired bpm: 64

(1 - (64/96))*100 = 33.333%
so you would have to make the sample slower by 33.333%

actual bpm: 99
desired bpm: 33

(1 - (33/99))*100 = 66.666%

so you'd have to make the sample slower by 66.666%

last check with same bmp

(1 - (64/64))*100 = 0%


of course some people will now say "what's all that math about" but here i explained the calculations behind what some programs do automatically.. ;)
 
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