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About this video
Teaching a computer to listen.
Andrew Robertson is designing software that can monitor and follow the tempo of a live drummer.
Rather than the performer following exactly a pre-defined “click track” the system allows computer controlled samples and effects to be timed according to the drummers own pace. Via a process called “time-stretching” the software is then able to speed up or slow down sound samples without altering their actual pitch.
In his second Components film, Andrew puts his software to the test at Queen Mary University London with a professional drummer and explains how the technology might be used creatively in musical performance.
- The Royal Academy of Engineering
- Andrew Robertson
- London, UK
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The evolution of technology has influenced the way we create music. Computers are smarter than they've ever been before, and they have become essential to modern music production and live performance. But where do we go from here?
I'm a research fellow looking at synchronisation in live performance. This is how you might get technology to respond and listen to live musicians as they play. But in order to do that, we need to teach the computer to listen.
Some bands might want technology to play an important part in their live show, for instance the samples and sequences that are there in the studio are playing. And in order to do that commonly at the moment, they use a backing track. And that generally involves a drummer listening to a metronome click that's in his ears.
And effectively you're then a slave to that technology. You're following a fixed metronomic pace. And the music isn't really live in the sense that we know, if you think of old bands like Led Zeppelin or the Rolling Stones.
So I started doing research here at the Centre of Digital Music Queen Mary University in London, in a system that would follow the drums, basically. On the basis that the drums are central to a rock and roll band. And that's probably what the musicians follow. So if we get the system to follow the drummer, you're sort of replacing that click track, essentially. The click track that used to maybe have to be listened to by the drummer, that would listen to him instead, and follow him.
Sound travels in waves, rather like the ripples in a stream. And the distance between the peaks of those waves is the wavelength. That determines the pitch that we hear.
So if we want to change the speed of sound, ordinarily you might just play it faster. But that will change the pitch, like on a record player. Instead we use something called time stretching, where we chop the sound into grains, like this ball. And then if we want this piece of sound to be shorter, we'll just remove some of the grains. And it will go faster, but each of them at the same pitch.
Well I've effectively got the sequencer running, which is the backing music. And the click track gets fed in. So you're monitoring both the drums coming in and it's own internal click. And I'm also looking a bit at how it handles these patterns.
Because he's an interesting drummer to have play. He's not just doing a very basic beat, more of a funky kind of syncopated thing than just, say, a straight rhythm. I think that's why it's an interesting test case to get this to look at it.
Dave the drummer is the one running. And that's me on the bike, represents the click track. He can't speed up or slow down because he has to stay in time with me.
If the drummer does speed up or slow down, he won't stay with the steady click track, and the sound will be out of sync. What my software does is allow Dave the drummer to go as fast or slow as he likes. By time stretching, the click track will stay in time with him.
In the studio, I'm testing how well my software can keep up with a real drummer. So I've asked him to try changing tempo to see how well he thinks the click track keeps up with him. Part of the problem is he's too good. Drummers are so well trained to adhere to click tracks that being in charge one, instead of it being in charge of you is a very alien concept.
I think what's interesting about this is it could eliminate the drummer having to be a slave to a click track in his ear. The drummer can kind of keep a steady-ish tempo. This system will be able to follow what the drummer is doing.
I think in terms of results it's interesting to hear Matt talk about technology. It's not something he's used to, really, a backing track that moves. I suppose beyond this, you'd want to go and see how it works in a band, in a live setting, and see what creative uses do people want to put it to. Can they create a hybrid kind of music, where you've got live musicians and some other more sample or computer-based stuff going on?
Well the system isn't yet perfect, and there's still work to do. But for now, I'm happy. If you're interested to know more about my research or want to try out this software, feel free to contact me, Andrew Robertson, at Queen Mary University of London. You can also visit the website. That's b-keeper.org.
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