Getting tempo info.

[Penguin]

Hi folks, I newbie question.

When I load a wav file into Audacity, is it possible to get to know what tempo (Beats per minute), bar (4/4) and so the track is?

If it is possible to get some of these info, how do I do it?

Thanks in advance.

[kozikowski]

I wonder if you couldn't trick Effect > Change Tempo into telling you the BPM...

Koz

[steve]

The only way that I've found is to count the beats for a few bars, select the area, and look at the length in the selection toolbar (tick the "length" check-box), then the BPM = (number of beats/time in seconds) x 60

Personally I would find it very useful if the timeline could be configured to show beats and bars, even if the BMP and beats per bar had to be entered manually.

[Penguin]

I wonder if you couldn't trick Effect > Change Tempo into telling you the BPM...
Koz

Hey Koz, I don't think so, once you don't know the original Tempo from the file. So any tempo you add in to change won't make difference. I'd like to know the original Tempo from a file. Thanks anyway for your reply.

[Penguin]

The only way that I've found is to count the beats for a few bars, select the area, and look at the length in the selection toolbar (tick the "length" check-box), then the BPM = (number of beats/time in seconds) x 60

Personally I would find it very useful if the timeline could be configured to show beats and bars, even if the BMP and beats per bar had to be entered manually.

Hi Steve, how do I know the number of beats from a song with several instruments? I tried you calculations but it brought me results as 450 bpm, but the sound looks like 90 bpm. :0)

[tommyd]

Sounds like a feature request might be in order: an automatic Tempo Detector could come in handy.

How about this - you select a section of audio, tell Audacity how many beats the section corresponds to, then Audacity tells you the tempo in bpm.

Is it worth requesting something like that?

[steve]

Hi Steve, how do I know the number of beats from a song with several instruments? I tried you calculations but it brought me results as 450 bpm, but the sound looks like 90 bpm. :0)

You need to count the main "pulse" of the music.

For example, with a Waltz you would count:
1,2,3, 4,5,6, 7,8,9, ....
Note the grouping in 3's - this is because a waltz is in 3/4 time (3 crotchets to a bar)

For a Military March you would count:
1,2,3,4, 5,6,7,8, 9,10,11,12, ....
The grouping here is in 4's because a Military March is usually in 4/4 time.
There may also be notes between these beats, like this:
1,and,2,and,3, 4, 5,and,6,and,7, 8, ....
but we still count the main beats, not the notes in between.

Dance tracks are often 2 beats to the bar, so if we had:
Bum - di - di - Bum - di - Bum - di - di - Bum - di ....
We would just count the main beat (the "Bum")
1, (di - di), 2, (di), 3, (di - di), 4, (di).....

Lets say that we count 16 main beats in a section that lasts for 12 seconds -
Our tempo (BPM) would be (16 divided by 12) times 60 = 80 BPM

This may help: http://en.wikipedia.org/wiki/Beats_per_minute

Sounds like a feature request might be in order: an automatic Tempo Detector could come in handy.
How about this - you select a section of audio, tell Audacity how many beats the section corresponds to, then Audacity tells you the tempo in bpm.
Is it worth requesting something like that?

http://www.webm.dk/node/7
Although, with a bit of practice it is very easy to work out, and with a bit more practice you will be able to "guess" the tempo fairly accurately without even counting.

[tommyd]

Although, with a bit of practice it is very easy to work out, and with a bit more practice you will be able to "guess" the tempo fairly accurately without even counting.

Sure, that's understood...but sometimes "fairly accurately" isn't good enough, and if I were cataloging a large number of loops (for instance) it'd be quite time consuming; an automatic tempo detector would be quick and precise.

If I'm only person who thinks it'd be a good idea then it's probably not worth me making a FR, but if other people are keen too then I'll post something.

[steve]

...but sometimes "fairly accurately" isn't good enough, and if I were cataloging a large number of loops (for instance) it'd be quite time consuming; an automatic tempo detector would be quick and precise.

The manual calculation method described previously is by far the most accurate method. Automatic BPM detectors do exist, but they only work on certain kinds of material as they depend on having a strong, clear and definite beat - a gentle flute or synth pad sample for example would fail completely.

If the samples are "ready to go" loops (all the editing and trimming has been done). then provided that the loop points are at the start and end of the loop, then you can simply calculate the BPM from the length of the sample. From a casual listen you will know if it's an 8 beat sample or a 16 beat sample, and you will know if it's around 120 BPM or 240 BPM, so you do the calculation "(beats/length) x 60" and if you get an answer of 236 BPM, but you know that it should be about 120 BPM, then obviously the correct answer is 118 BPM.

Perhaps if the time bar had more options -
As I said before, I would like to see an option of setting "number of beats per par" and BPM, then having the time bar display "beats and bars". This would also be a very quick way that you could check if a loop is the BPM that you have it catalogued as, and a quick way to check if two samples have the same BPM.
If there was also the option to display in minutes (with several decimal places), then your calculation would become much easier - just "number of beats/length".

[Penguin]

You need to count the main "pulse" of the music...

Hey Steve, thanks a lot for your time and for sharing this tip. Very useful post. I appreciated that.

Have a nice weekend.