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Time stretch in audio is one of Live's best known features. Let's take a look at how Live analyzes, and processes audio in order to time stretch clips, and learn to choose a warp mode that matches the musical situation. So, changing the tempo of an audio clip or an audio file was not a really useful thing until we could do that without actually changing the pitch of the contained audio. So, let's see how that works in Live. So, I'm going to choose this first clip that I've got here on this audio track. And for Live to time stretch the audio contained there, we actually need to have the Warp button enabled. Now, if this audio clip was brought into the session and that Warp button hadn't been on.
The audio will just play at its original tempo, which we can see in this case is 110. What Live will do as soon as that warp button is enabled, is that it will analyse the clip and it will look for transients. And from that, it will calculate tempo and length information. Then it actually saves that as an additional file. Now I'm going to Cmd+tab out to the finder, just so I can show you that inside this project file, there is an audio file called demosong.aif. And then just below that, there is another file that ends with a .asd distinction.
And that's that analysis file that contains that analysis of the transients and their location. And in the end, the tempo and the length information that Live has guessed from analyzing the file. So, again, we've got the Warp button enabled, and I should be able to play this clip, and then change the tempo. And we should be able to hear that as I speed up and slow down the clip. Let's try it. (music playing) And so we, we learned a lot from hearing that, because as I moved it a lot slower we actually started to hear some funkiness intrude there.
As the sample started to get so far apart that Live was having trouble kind of maintaining the integrity of the sound of that clip. When I move faster we didn't hear any problems at all because the actual pieces of audio that are contained for each transient actually get moved closer together. So, how does Live handle that? Well first of all, Live uses different algorithms for different kinds of audio. So anything that you're doing with a drum clip or, that has sharp transients to it, you're going to want to use what's called Beats Mode. An if I click on that you can see that we've actually got about six different modes.
As you choose a mode, you'll actually get different parameters that appear just below that. So, in this case the preserve option gives us two different modes. We have transient, which uses the transients in the audio clip to determine how it's going to warp it. Or, we can switch to a different rhythmic value, and in that case, Live will try and preserve the specific beat divisions that are contained within that file. I actually like Transient modes, I think it works the best, so I'll choose that. And then I'm going to drop down to this next chooser, which allows us to see the loop mode. The first one if called off, and what that means is that when you play it, it's going to play each segment or each transient, any decay. And then it's going to stop when it gets to the end of that, and it's going to wait until the proper time to play the next segment. So, this is a great example of showing you what happens when you slow down a clip.
So, again I'll play this and I'm going to slow it down, you know 30 or 40 BPM. (music playing) So you can actually hear it play that piece and then wait for the next one before it moves on. Now the other two options that we have here are called Loop Forward and Loop Back and Forth.
So what Loop Forward does, that's the second one here. Is it will, play each segment, and then when it gets to the end, it will jump back to the middle. And then it'll play it to the end again, jump back to the middle, until it's time for the next segment to play. The loop back and forth which is the last one. It will actually play to the end of this segment, and then play backwards towards a point, near the middle. And then it will play it forwards again until it's time to play the next segment, and to me that's about the most natural one. So I'll choose that, and then this last setting here is a transit envelope sets a fade length. Now longer times are going to give you a much smoother transition between one segment and another one.
And shorter times will result in a gating like an effect. So, if I set this all way about 100 there is no fade, and down at zero I'll get each segment decaying very quickly. All right, for different kinds of audio you're going to want to use a different mode. So, the next clip is a base clip and on this one I would use Tones mode, which is good for monophonic type material which would be like a base line, maybe a guitar solo or perhaps a vocal. And the only option that we get with that particular mode is this green size. And what the people at Live tell us is that as it time stretches the audio it divides it into short segments that are referred to as grains as if the whole audio clip was a big pile of sand.
In some cases, you're going to want to choose a very small granular size. And in others, you're going to want to choose a larger grain size. And using their guidelines, they say that, use smaller grain size for content where the pitch is really clear. And larger grain size when it's not. So, let's give a shot at this, and just hear what it sounds like. (audio playing). Now I've dropped the tempo so slow, that I'm going to stop and I'm going to boost that backup, the original BPM is around a 100. So, lets do that about 90, and lets here it stretch at that point.
(music playing) You can see that when I got the grain size down to a smaller grain size it actually started to clear up and it sounded better. Some of the other modes that we have here would be Texture. That's good for polyphonic material like pads of synth parts or maybe strumming guitar parts. With the Repitch mode, there is actually no time stretching. Instead, it fits the clip to the tempo by changing the play speed. So, let's try that one on the third clip here, and hear what that sounds like. (music playing) So you could actually hear the pitch of the clip changing as I was changing the tempo.
The last two options here, we have our Complex and Complex Pro. And these are really good for warping or time stretching really long pieces of audio, like you're trying to do a whole song. Or something where you really want to pay attention to the real detail with the clip. In most cases I would suggest using the newest option which is Complex Pro. So, let's take a look at the last clip, which is a piece of the demo song that we have as part of this course. And I'll switch that to Pro, and one of the options that we get here is for formants.
Now, formant frequencies are that part of a sound, for example with a, a sax the formant frequencies would be derived from the actual length of the tube and the shape of the tube. And when you time stretch or transpose a file, those format frequencies can get transposed with that, and it's what gives us that chipmunk effect. So, Ableton actually gives us the ability to kind of lock those formants in place. Or at least adjust them so that as we time stretch or change the pitch. We actually don't get nearly as much of that chipmunk effect as you might otherwise get.
So, let's go ahead and play this, and I'll change the tempo on this one, and let's hear how it works with this entire song. (music playing) And you hear it's pretty successful at that. I actually started that about 40 BPM lower than the original tempo, and it still had the, the integrity to it. While this time stretching process is not perfect, Live's audio time stretching is so effective that it makes using clips of different tempos in the same song easy.
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