Need to Slow Down?

Often I want to slow down a sample and make a texture pad from the result. Or perhaps when I’m looking for an interesting loop found through planned happy accidents. But at a certain point you can actually run into some limitations by how digital audio is captured. By stretching it with most typical audio software, you will start to hear the quick shifts in tone instead of a the subtle gradients that you would hope for. So for a long time, I assumed this could only be achieved with expensive and dedicated hardware. But once again the open source movement comes to the rescue with a piece of software called PaulStretch.

With PaulStretch you can easily stretch audio anywhere from 50x to 10,000x… or even with hyperstretch mode: 1,000,000,000,000,000,000x. Holy smokes! And you can hear the playback in realtime without intensive processing just to hear it! Its easy to turn 5 minutes into 5 hours. And this software does an incredibly smooth job. It is so much fun to play with.

So how is this possible?

This program doesn’t process the sound as a single piece: it cuts the sound in small pieces and process them. Each small piece is called a “window”. The size of the windows controls the size of the window in samples, which affects the frequency and the time resolution of the resulting sounds. The small windows have good time resolution, but poor frequency resolution. Also, large windows has poor time resolution, but they has great frequency resolution. Usually, a window of 7-12k is good for most music. Very big windows (larger than 100k) can be used for special effects (for smearing the sound very much and transforming it into a sound-texture even if the stretch is closer to 1.0).

I’ve enjoyed playing around with this and using them for instruments within Renoise. Its also been fun to stretch some of my favorite songs and to my pleasant surprise suddenly hear a sample that had been sped way up.

Check out some examples of the extreme stretching below.

Here is the windows installer (sorry no mac love!). Or if your really interested, here is the sourcecode.

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I'm interested in aleatoric music that involves some type of random chance and automated computer processing. I'm just curious to see what a powerful machine will run with when given an algorithm. But I love collecting and listening to all genres of music on some good speakers. Most of my time is spent working as a Science Visualizer at the Charles Hayden Planetarium.

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2 thoughts on “Need to Slow Down?

  1. ben says:

    Is this similar to granular synthesis/sampling? The explanation of the “windows” sounds a lot like grains and how granular synthesis works. Very cool stuff.

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