Granular Sampling with Ableton Live
Let’s talk about granular synthesis, or more accurately, granular audio processing. I find the term “synthesis” a little…misleading. You see, the resultant waveform is generated by the granular process, unlike a periodic electronic signal generated by an oscillator. Regardless of whether it’s an audio effect or a sampler instrument, the “grains” are actually snippets of audio processed within a highly sophisticated sample playback engine.
There are a number of ways to “granualize” audio. The result depends on the source material, any combination of parameter changes and obviously the granular engine itself. But don’t despair. Even though there are many powerful (and occasionally somewhat expensive) granular instruments and effects available on the VST market, you can produce surprising results in your DAW’s sampler.
Now, since we’ll be using Ableton Live in this tutorial, I should point you in the direction of Granulator, made by German electronic musician, sound designer, audio engineer and Ableton Live co-developer Robert Henke. We’ll be doing something considerably more primitive than what you can do within that free Max for Live instrument, but that’s basically the whole point.
Ableton Live’s “Simpler” and “Sampler” instruments are ideal for this tutorial, in which we’ll look at a few different ways to granulize audio with a variety of modulation options and warping controls built right into the instrument. The first thing we’ll experiment with is creating a “grain cloud” within Sampler.
I first start out by choosing a sample rich with harmonics. Something like a resonant bell or a guitar. Nothing like a drum loop with a lot of transient data. You want something with a long release so your dynamic can be “cherry picked” by the jittering grain window. For example, I’ve chosen a tube chime, which is sampled from a homemade instrument I built from windchimes a few years ago.
Once I’ve chosen the sample I want to granulize, I make sure I have both the “Link” and “Sustain Loop” buttons switched on so the loop begins immediately. The loop itself can be as small or as large as you want, but I prefer a grain window between 50-100 milliseconds. I usually turn the Crossfade level up a bit to remove unpleasant DC offsets often produced by sudden loop transitions. I prefer a linear crossfade, so I just deselect the “Use Constant Power Fade For Loops” option that appears in a context menu when you right-click on the Device Title Bar.
In the Modulation tab, activate LFO 2, then select the “Loop Start” target within the “Destination A” slot. This is where all the magic happens. Select the “Sample & Hold” waveform within the “LFO Type” box and then tune the LFO speed to a Frequency near audio-rate. This will randomly shift the “Loop Start” position, producing that jittery behavior we’re looking for.
I’m using a sample recorded on a Shure SM58 dynamic microphone, so it’s a bone dry mono signal. I want to create a bit of movement by modulating the global pan position, but I need to avoid modulating the “Panorama” target with LFO 2 since audio-rate modulation produces intermodulation artifacts whenever assigned to that parameter. Instead, I just use LFO 1 with a triangle wave at 2 Hz.
In the MIDI performance tab, you can further modulate the “Loop Start” target with Aftertouch or Mod Wheel assignments. I like to use a negative modulation depth. That way, the Mod Wheel nudges the “Loop Start” toward the beginning of the sample wherein there are (normally) harsh high frequencies in the attack transient. This is a great way to sprinkle in nuanced textures on the fly.
Now we have our standard issue “grain cloud”, which is something you could easily program within the Granulator instrument I mentioned earlier. Obviously, there are advantages to using something clearly more powerful than just Ableton’s Sampler, although Sampler is significantly more CPU friendly than Granulator, and you can duplicate Sampler in a multi-sampled instrument without taking a huge hit.
The next thing we’ll look at is slightly more experimental. Ableton Live’s sophisticated time-stretching algorithms built into the warping controls (in both the Clip View’s sample box and in Simpler) make use of a grain window similar to the loops we were experimenting with in Sampler, except the grains behave a bit differently depending on which algorithm you choose.
In Beats Mode, the “transient loop” is triggered upon transient detection. Remember when I said to avoid anything with a lot of transient data? Well, this time, we’re going in the polar opposite direction. Live’s Warp Modes eat transient data for breakfast. In Beats Mode, you can use a Transient Envelope with the “Loop Off” option, which will play back audio between transients and then stop, or you can use the “Loop Forward” or “Back-and-Forth” options in the same way that Sampler’s Sustain Loops work. Also, you can switch between transient detections and beat detections in note values of ½, ¼, etc.
This type of granular re-synthesis becomes a little more noticeable when you halve the playback speed of the sample or even halve it a second time by using the “Double Original Tempo” button. Depending on the size of the grain window, the result will vary, but I’ve found this technique especially “stuttery”.
The Tones and Texture Modes are a bit similar, although they do behave very differently. Both modes have a “Grain Size” knob, but Tones Mode will adjust the grain size in a signal-dependant manner that depends on the clarity of the pitch contour of the sample in use. In Texture Mode, the grain size will be left unaltered. Also, there’s a “Flux” parameter (in Texture Mode) that will impose a bit of randomness on the grain size, which is slightly more noticeable when the grain size is set to a considerably high value.
The remaining Warp Modes aren’t designed for granular applications, so we don’t need to mess with those. I tried to come up with some sort of “just add water” recipe that produces similar results every time, but this approach is so reliant on the source material, I kept bumping into happy little accidents almost every time I tried to create the same result with the same settings on different samples. So, these warping controls are ideal for experimental use.
Of course, I’m just scratching the surface of what’s possible here, especially when you can take things even further with Granulator. I just think a lot of people underestimate what you can do with your DAW’s factory plugins, which are often significantly more powerful than you might think.