Determining the BPM of a loop

[kwiksilver]

A friend of mine sent me a series of tracks that were recorded with a percussion loop. He recorded the tracks with the loop in real time but never made note of the BPM.

I want to toss the percussion loop and use a click track.

I downloaded a 100 BPM groove stick click from the Sonar forum that is supposed to stretch from 80 – 120 with no problems.

Using an aural comparison between click and loop, a BPM of 122.30 seems to be right on to my ears. But I could be off by any number milliseconds.

Question: Is there a BPM calculator available that can determine the exact tempo of an audio clip or groove (acid) clip?

I already downloaded "Beat Monitor" and couldn’t get it to work. Probably because the program doesn’t have an option for ASIO drivers.

Thanks for any suggestions.

kwiksilver

[otek]

If I receive an unknown loop of some description, I usually fist make sure that the start of the file is also right on the "one" of the loop.

Second, I find out how many bars the loop is, and in what time signature.

Third, I line up the start of the file with the first bar mark, using whatever form of "snap to grid" function that's available to me.

Fourth, I adjust the tempo of the song until the bars and beats seem to roughly line up with the audio. I then zoom in close on the end of the loop and fiddle with the tempo until it lines up with the last ppq of whatever happens to be the last bar - usually #2 or #4.

I then listen to the audio and make sure the beats appear to sit right with the system click.

Remember the loop starts over after two or four bars, so it's not like you're gonna experience any drift. Just make sure it feels right for what you are trying to do.

I often use the groove-to-midi quantization to then quantize any additional rhythmic elements with the first groove - unless I'm looking for the tension between two slightly different grooves (this is of course in case I am programming).

[eagan]

Jot this down somewhere, although it's easy to remember.

With tempo being "beats/minute", a quick juggle gives you:

60/tempo=seconds per beat

Multiply by number of beats in a bar, you have length of one bar in seconds.

In other words, this simple little formula is simply a quick algebraic juggle converting "beats/minute" to "seconds/beat".

And of course, the reverse works, so for your question;

60/seconds per beat= beats per minute

...and there's your tempo for that mystery loop.


JLE

[Jason Phair]

Otek is the master at figuring out and working around fucked up loops.


Hehehehehehe.

[Kenny Gioia]

In Pro Tools, I will put the loop on bar 1 and select the point where the next bar starts and hit "Identify Beat" and type Bar 2.

PT will manually put a tempo marker in that bar that will be your tempo.

[kwiksilver]

Thanks for the responses. I spent some time working on this over the weekend.

I still consider myself a novice at this so I may be giving you way too much information.

otek:

My friend also sent me a mix of the tracks. The percussion loop is actually a wav file. It is only one measure in length (as far as I can tell). I assume the ppq doesn’t apply since it is not a MIDI file.

When I right-click on each track and looked at Clip Properties-Groove Clip tab, there is a grayed out field that shows the Original tempo. The tempos for the tracks ranged from 120.8 to 121.77 or so. I assume those numbers are meaningless since the tracks are audio.

The percussion track shows an original grayed out 93.xx (I’m not at my home computer at the moment). I’m guessing it was originally a loop or a clip that was enabled as a loop and stretched.

I did a lot of experimentation. Got real frustrated at times because the downloaded click I used seemed to be slightly off and I couldn’t get it to nudge properly. I even sliced off a few milliseconds to no avail.

At one point I decided I didn’t want the changes I made and shut down Sonar without saving the project. When I went to open it again the next day, Sonar says the file is not compatible with this version. WTF. It turned out to be not a big problem though, because the audio files were still intact. I had to re-import them into a new project.

So yesterday I did the visual option as you suggested. Zoomed in on the waveform and lined up the measure using the tempo toolbar and changed 1 decimal point at a time until it lined up. The tempo ended up at 122.32. I then inserted a two measure count-in I had created a while back. Loop enabled it and stretched it out the length of the percussion track. So far so good. Sounds pretty damn close to my ears.

I then recorded two tracks for sixteen measures while listening to the percussion loop. One track just chords and one single root notes.

At that point I started to insert the other tracks one at a time to see if they lined up with the recorded tracks and the percussion track.

Working well so far. If there is any drift further on in the song, it will probably be from the player.

My friend recorded all 6 tracks fairly quickly and considered them scratch tracks.

I want to be able to cut and paste some his tracks to rearrange the song and send it back to him.

eagan:

Math was never one of my good subjects. After working out the BPM as mentioned above, Sonar shows one measure to be 1 sec, 29 frames long.

Assuming that 4 beats per measure works out to be 1.97 seconds long, then I got these results depending on how many decimal points you use:

1.97/4 = 0.491675

122.0318
122.0331
122.0504
122.1996
122.449

So I’m some where in between the last two.

Kenny:

I don’t own Pro Tools and I don’t think Sonar has that option.

Thanks again.

kwiksilver

[otek]

I assume the ppq doesn’t apply since it is not a MIDI file.

Sorry, I was a bit careless with the terminology. I use Logic, and in the arrange window, Logic snaps to 240 "steps" per quarter note, same as the MIDI ppq's.

It doesn't matter. What I meant was to get it as close as possible, that's all.

The tempos for the tracks ranged from 120.8 to 121.77 or so. I assume those numbers are meaningless since the tracks are audio.

It sounds to me like Sonar has a function that calculates tempo from a given audio file by analyzing the position of the transients. I believe this is possible in Logic too, although I am uncertain how it's done.

So yesterday I did the visual option as you suggested.

It seems that, if the transients are reasonably sharp, visual would be the way to go, at least to begin with - you can always listen back and fiddle with it later.

But here's what I'm not getting, and forgive me if I am missing something crucial, but it seems you are making all this unnecessarily convoluted for yourself, by importing some click and stretching it, etc. Why do you need to do that? Why don't you simply set Sonar to bars and beats, set the tempo of the song to match the loop as you got it, and snap the loop audio to even bars? Why don't you check it with the on-board metronome click in Sonar (which adjusts to the song tempo) instead of some mysterious downloaded click?

Again, sorry if I'm missing something here.

:Confused:

[kwiksilver]

But here's what I'm not getting, and forgive me if I am missing something crucial, but it seems you are making all this unnecessarily convoluted for yourself, by importing some click and stretching it, etc. Why do you need to do that? Why don't you simply set Sonar to bars and beats, set the tempo of the song to match the loop as you got it, and snap the loop audio to even bars? Why don't you check it with the on-board metronome click in Sonar (which adjusts to the song tempo) instead of some mysterious downloaded click?

Again, sorry if I'm missing something here.

:Confused:

My low level of expertise with Sonar prompted me taking a convoluted path amongst other things.

The Snap to Grid function in Sonar always frustrated me somewhat because some clips moved were not always dead on where I wanted them. I did some research and found an article by Craig Anderton in Sound-on Sound where he suggests changing Sonar’s default settings by unticking ‘Snap to Audio Zero Crossings’ and using the ‘Move To’ instead of ‘Move By’ option.

As you suggested, I tried the on-board metronome and it worked fine. Just never thought about using it.

A few things in the song threw me a curve.

Some parts he plays are fairly syncopated and they tend to sound like a different time signature played against 4/4.

The last verse in the outro of the song comes in on beat 3 of the measure after a two beat rest.

Anyhow, I’m at a point where I can delete the percussion track.

Thanks again.

[otek]

The Snap to Grid function in Sonar always frustrated me somewhat because some clips moved were not always dead on where I wanted them.

Now, I'm not a Sonar Jedi like Pimp-X or Fulcrum (we should have them weigh in for good measure) but just by reading the terminology, it's my conjecture that:

a) The "Move To" option will snap the selection to a bar, regardless of what its starting point is. This can be a problem if edits were made on a file, or if the file started recording, off the bar lines.

b) The "Move By" option will move the selections in one-bar increments (increment size naturally depending on snap settings), so that the selection will start in exactly the same relationship to the bars and beats.

c) If selections behaved a little whimsical, it is most likely that you weren't zoomed in enough to be able to make accurate moves - you moved selections slightly to the side without noticing. I will hereby recite the Spiderman credo - With Great Power follows Great Responsibility! :D Always, always make sure you are meticulous about how you move things around, Grasshopper. Be sure you are using the right snap properties when moving things zoomed out.

I don't know about Sonar, but in Logic, there is a mode called "Smart Snap" which sets the snap according to your zoom level.

d) Again, if you align the start of your loops properly to the start of the selection, and always move by even snaps, none of this has to happen.

I did some research

Also, Reading The Fucking Manual is a great way to learn the ropes..... you do have a manual, right?

Some parts he plays are fairly syncopated and they tend to sound like a different time signature played against 4/4.

Sometimes the loop simply doesn't sound right with a certain beat, and it may be a good idea to alter it, or take it out altogether. In this case, you scrapped the loop entirely, but given that the drummer is tight enough, keeping the loop may be a great groove enhancer.

The last verse in the outro of the song comes in on beat 3 of the measure after a two beat rest.

That's easy. Simply move the loop to start one beat earlier, and you're back on track.

Anyhow, I’m at a point where I can delete the percussion track.

Whaaaaat?!?!?! All this trouble for nothing?! You bastard!!!

Evil! :D :lol: :Wink:

[Brendo]

Otek,

I want to toss the percussion loop and use a click track.

[Tim Halligan]

I will hereby recite the Spiderman credo...

Is he posting here now?

:lol:


Cheers,
Tim

[otek]

Is he posting here now?

Yeah, isn't he the burly guy with the east coast accent on the Mixerman Radio Sh.....


Oh.

[lebouche]

It sounds to me like Sonar has a function that calculates tempo from a given audio file by analyzing the position of the transients. I believe this is possible in Logic too, although I am uncertain how it's done.




The plug in on Logic 7.2 just counts bpm and is called bpm counter...you just insert it on the track and press play. If anyone ever gets this stuck just pm me the audio it only takes a min.