The synth below is reading a short recording of guitar chords. Hold the note: you'll hear the chords drift past, a little softened and shimmery, but recognisably the recording. Now drag Scan to zero.
Before you do: the part of the engine that moves through the recording is about to stop. Will the sound stop, stutter on one spot, or keep going?
Drag Scan to zero while the note holds. Does the sound stop, stutter, or keep going?
Freeze a moment
What just happened?
The sound kept going. The chord froze in place, but it didn't turn into a stuck, stuttering loop. It kept breathing, like a sustained chord. Watch the spectrogram: the picture stops changing shape, but it never goes still.
That's because a granular engine doesn't play a recording the way a tape or a sampler does. It cuts it into tiny overlapping slices called grains, here about 150 milliseconds each, and plays dozens of them every second, each with its own soft fade in and out. Two separate things are moving:
- Each grain plays its little slice at its own speed, which sets its pitch.
- The read position, where the next grain will be cut from, moves through the recording at a separate speed, set by Scan.
When you stopped Scan, only the second movement stopped. New grains kept being cut from the same moment and kept playing at normal speed. So the pitch and colour of that moment carried on, while time stood still.
Where the engine reads
Slower without going lower
On a tape machine or a turntable, time and pitch are chained together. Slow the tape to half speed and everything drops an octave: the familiar slowed-down voice. Most people assume that's what slowing a sound always does.
Set Scan to 0.5. The chords now unfold at half speed, twice as long, and the pitch doesn't drop at all. Try 0.25, or a small negative number to drift backward through the recording. Then move the Pitch control in the full panel: the pitch changes, and the speed doesn't. In a granular engine, time and pitch are two separate knobs. That's the trick behind a lot of time-stretching, and behind the slow, glacial, still-recognisable textures of ambient music.
Size: how much of the moment each grain carries
Size is the length of each grain. Try it with Scan at zero.
Longer grains, 200 to 500 milliseconds, carry more of the moment: you can hear little pieces of the strum, a hint of movement inside the freeze. Shorter grains, 20 to 50 milliseconds, carry less: the sound turns smoother and more abstract, but also grainier, a fizz instead of a chord. Somewhere around 100 to 200 milliseconds is often the sweet spot for a held pad that still sounds like its source.
Density and spray: how many, and from where
Once you've played a note, two more controls appear.
Density is how many grains start each second. Low density with short grains gives you separate little blips, like rain on a window. Higher density lets the grains overlap into a continuous cloud.
Spray lets each grain start from a slightly random spot around the read position, instead of exactly on it. A little spray makes a frozen moment breathe more, because each grain is slightly different. A lot of spray pulls in neighbouring chords and strums, and the freeze turns into a slowly churning cloud of the whole region.
Where the ideas come from
The idea that sound could be built from tiny particles goes back to the physicist Dennis Gabor in the 1940s, who described sound as made of "acoustic quanta". Iannis Xenakis made music from it with tape splicing and tone generators. In the 1970s and 80s, Curtis Roads and Barry Truax brought it to computers, and Truax made it run in real time. Today it lives in everything from DAW plugins to hardware like Mutable Instruments' Clouds module, whose Freeze button does exactly what you just did with Scan.
Where it breaks
The buzz. Set Size to its smallest and Density to its highest, with Spray at zero. Listen for a new, rough pitch that wasn't in the recording. When grains start at a perfectly regular rate, that rate itself becomes audible as a tone or a buzz. If a frozen pad suddenly sounds like it's humming a note of its own, lower the density, lengthen the grains, or add a touch of spray to break up the regularity.
The wrong moment. Freeze on a silence and you get silence. Freeze on the pick attack and you get a restless clicking. Freeze between two chords and you may get a muddy blend of both. Before adding any effects, move Position slowly with Scan at zero and listen for the moment that holds best: usually the body of a chord just after the attack, once it's settled.
Too much spray. Spray pulls in material from around the read position. If a different chord suddenly wanders into your frozen pad, you haven't broken anything; that chord was just within reach. Pull spray back.
Same idea, different place: a spectral freeze also holds a moment forever, but it slices by frequency instead of time: it captures the balance of frequencies at one instant and keeps re-synthesising it. Granular freezes have a grainy, breathing life; spectral freezes have a glassy, smeared stillness. Same goal, different ingredients, different textures. See Spectral effects.
Make it yours
Open the full panel and pick a different Take: the single notes, the slow noodle, or the long picking. With Scan at zero, drag Position slowly until you find the one moment that makes the best held texture. Then turn up Spray and Pitch Jitter, and add just a little of each: a few percent of spray so the moment breathes, and a small pitch jitter so the grains drift slightly around the note, like a choir instead of one voice.
Play chords on the keyboard. Your frozen moment is now an instrument. When it feels like a pad you'd want under a track, open Granular from the link at the top of the lab, which carries your settings, and save it, with the take and the moment in the name, like "Long Picking at 0.62, breathing".
Quick check
- You set Scan to zero and the sound keeps going. A friend expected silence. How would you explain it? Scan only moves where the next grain is cut from. The grains themselves keep being made and played, so the moment keeps sounding. It's the reading that stopped, not the playing.
- You want a guitar phrase to last four times longer without dropping in pitch. What do you change, and what do you leave alone? Set Scan to 0.25 and leave Pitch at zero. The read position crawls through the phrase while every grain plays at normal speed.
- Your frozen pad has a strange low hum that wasn't in the recording. What's the likely cause, and the fix? Very regular grains: the grain rate itself has become audible. Lower the density, lengthen the grains, or add a little spray so they don't all arrive in lockstep.
Next steps
- Go deeper: Physical modeling. Grains can borrow the colour of a real guitar, but they can't make a string you never recorded. What if you simulate the string itself?
- Sideways: Tagging, search and similarity. A model can lay a folder of sounds out as a map where neighbours sound alike. Walking that map is another way to choose what to play.
- Explanation: Pitch shifting. Changing pitch without changing speed, and what it costs.
