Re-Cumulonimbus

A granular delay · Re- series · Vulpus Labs

Re-Cumulonimbus is a remake of Cumulonimbus, rebuilt from the ground up. It does everything Cumulonimbus did, without its faults, and adds a random clock of its own, random spread on position, pitch and pan, reversed grains, pitch quantising, a trigger out at each grain, and CV amounts on every control.

For Cumulonimbus users, below, lists what has changed.

Re-Cumulonimbus records its input continuously into a memory a few seconds long, and each time it is triggered it plays back a grain: a short piece of that memory, from 10 ms to a second long, taken from a chosen point in the past, at a chosen pitch, faded in and out, and placed in the stereo field. Up to 64 grains play at once. Fire them slowly and you hear echoes and stutters; fire them fast and they blur into a cloud of texture, a shimmer above the input or a smear below it. Freeze the memory and the grains go on picking through what it holds.

To begin: patch a sound into IN L, and OUT L and OUT R to your output. Turn DENSITY up to about half way, so grains start about ten times a second, and SPRAY and WIDTH up a little. A cloud of what you have just played forms around the input. Turn PITCH up for a shimmer, or FREEZE to hold what is in the memory.

How it works

The input is written continuously into a memory 5.5 seconds long. Each trigger, from TRIG, its button or DENSITY's own clock, starts a grain. The grain reads a piece of the memory once, with a fade in and a fade out, and stops.

Every choice about a grain is made when it starts, from the controls as they stand then:

• where it is taken from: POSITION back from now, moved at random by SPRAY;
• how long it is: LENGTH;
• its pitch: PITCH, moved at random by SCATTER, and snapped by QUANTISE;
• whether it plays backwards: with REVERSE's chance;
• how long its fades are: FADE;
• where it sits in the stereo field: PAN, moved at random by WIDTH.

Turning a knob changes the grains that start after it, not those already playing.

A grain pitched up plays through the memory faster than it is being written. So it starts as much further back as it will gain, and ends where POSITION says, never catching up with the present.

GRAIN

POSITION sets how far back grains are taken from, from now fully left to one second ago fully right. It loads fully left. Hover over it, as Position: 250 ms back.

LENGTH sets how long each grain lasts, from 10 ms fully left to one second fully right, evenly in ratio across the travel. It loads at the centre, 100 ms, as Cumulonimbus did.

PITCH sets each grain's pitch, from an octave down fully left to an octave up fully right, as a change in playback speed. At the centre, where it loads, grains play at their own pitch.

FADE sets how much of each grain is fade, from a tenth of each half of the grain fully left to all of it fully right: short fades give hard-edged grains, long fades soft swells. The fades are equal-power curves. It loads just under half way.

PAN sets where grains sit in the stereo field, from left to right; at the centre, where it loads, they come out as they went in. A grain placed to one side keeps both its channels: its middle moves across, and the difference between left and right stays.

CLOUD

DENSITY is Re-Cumulonimbus's own clock. Fully left it is off, and only TRIG starts grains. Above that it starts grains at random, from about one every two seconds to 256 a second, evenly in ratio across the travel. The timing is random, like rain: the knob sets the average.

SPRAY moves each grain's position at random, by up to half a second either way of POSITION. Fully left, every grain comes from the same place.

SCATTER moves each grain's pitch at random, by up to an octave either way of PITCH. The total is held within an octave up and down.

REVERSE sets each grain's chance of playing backwards, from never fully left to always fully right.

WIDTH moves each grain's place in the stereo field at random, by up to the whole field either way of PAN. Fully left, every grain sits at PAN.

LOOP

FEEDBACK sends the grains back into the memory with the input, so later grains play earlier ones: echoes of echoes, and pitched grains climbing or falling further each time. On its way back the sound is darkened a little and its lowest bass removed, and it is limited, so it cannot run away however high FEEDBACK goes. It loads fully left.

MIX fades from the input alone, fully left, to the grains alone, fully right, at equal power. It loads at the centre. Fully left is the input exactly.

TRIG, the button or the jack, starts a grain. The jack fires as it rises above 1 V and re-arms when it falls below 0.5 V, so a clock, a gate or an envelope will do. TRIG and DENSITY can be used together.

FREEZE, the button or its GATE, stops the memory being written. The grains go on playing what it holds, and a grain that reaches the most recent sound turns round and plays on backwards until it ends, so nothing runs off the end of what was recorded. Release FREEZE and recording resumes, fading in over 10 ms. The gate holds FREEZE on while it is above 1 V, and lets go below 0.5 V.

QUANTISE snaps each grain's pitch: OFF, to the nearest semitone (SEMI), or to the nearest of an octave down, a fifth down, unison, a fifth up and an octave up (5THS). It applies to PITCH and SCATTER together. With SCATTER up and QUANTISE at 5THS, grains form a chord.

I/O

LEVEL sets how loud the input is recorded, from silence fully left to twice its level fully right; at the centre, where it loads, it is recorded as it is. It changes what the grains play, not the dry signal.

QUALITY sets how grains off their own pitch are read, and so how much a busy cloud costs. It loads at HIGH.

Grains at their own pitch sound the same at every setting. Coming up from LOW, grains pitched up take a moment, a second or two at most, before they go back to the cleaner copy; until then what is above 12 kHz folds back, as at LOW.

START gives +5 V for 1 ms as each grain starts.

The grains' level is kept steady however many are playing: a dense cloud is about as loud as a single grain. The output is limited gently above 5 V and never goes past 10 V.

The display

The display shows the last four seconds of the memory, the newest at the right edge. The input's level is drawn faintly along it. Each grain playing is a spot where it is reading, its height its place in the stereo field (left at the top), its size and brightness its fade. Grains playing backwards, from REVERSE or from turning at the end of a frozen memory, are violet; the rest are amber.

Read together, the strip shows where in the past the grains are drawing from: with POSITION low they gather at the right; with SPRAY up they spread out; when FREEZE holds, the strip stops moving and the spots wander through it.

Jacks

Every input reads 0 V when nothing is patched. Each CV has an AMT knob beside it: with AMT at its centre the CV does nothing; turned either way it scales the CV, and at either end ±5 V sweeps the whole of the knob's travel.

Notes

Pitched-up grains do not alias at MED and HIGH. A grain an octave up plays everything in it an octave higher, and anything above 12 kHz would fold back down. Re-Cumulonimbus keeps a second copy of the memory with everything above 12 kHz removed, and grains faster than their own pitch play from that. At LOW the copy is not kept, which saves its cost.

Grains at their own pitch are exact. A grain at its own pitch plays back the samples that were recorded, without interpolation. Others are read between samples: by a smooth (Hermite) curve at HIGH, by a straight line at MED and LOW.

64 at a time. A 65th grain takes over the oldest, which fades out over 5 ms rather than being cut.

Pay for what you use. Each grain playing costs a little; a cloud of 64 costs the most. QUALITY at MED or LOW makes a busy, pitched cloud cheaper.

For Cumulonimbus users

• The memory is 5.5 seconds, not 1.4. Cumulonimbus's grains could reach past the end of its memory with POSITION and LENGTH high and PITCH up, and came back with the wrong sound and a click; nothing here can.
• Frozen grains turn round on purpose. Cumulonimbus's did too, by accident, and dipped to silence as they turned; here the turn is smooth.
• Dense clouds no longer get quieter. Cumulonimbus's output curve turned down above about 12 V, so many grains at once came out softer, and folded; here the level is kept steady and the limit is smooth.
• MIX fully left is the input alone. In Cumulonimbus the dry side carried the feedback and LEVEL too.
• PAN is a true pan, and a grain to one side keeps both channels.
• Feedback is filtered and cannot run away.
• TRIG fires above 1 V and re-arms below 0.5 V. Cumulonimbus fired on any rise above 0 V.
• Pitched-up grains do not alias, unless QUALITY is at LOW, which reads as Cumulonimbus did.
• CV has an AMT. In Cumulonimbus, a cable at 0 V moved a control half way towards its limit; here a CV adds to the knob, by as much as AMT says, and 0 V changes nothing.
• DENSITY, SPRAY, SCATTER, REVERSE, WIDTH, QUANTISE and START are new. With them all off, grains are started only by TRIG, as Cumulonimbus's were.

Starting points

A cloud. DENSITY at three quarters, LENGTH a quarter, SPRAY half, WIDTH fully right, FADE fully right, MIX half. Short, soft grains of the last moment swarm around the input on both sides.

Shimmer. PITCH fully right, DENSITY three quarters, LENGTH the centre, FADE fully right, FEEDBACK half, MIX a third. Grains an octave up go back into the memory and rise again, and a halo forms above the input.

Chord cloud. SCATTER fully right, QUANTISE 5THS, DENSITY half, LENGTH three quarters, FADE fully right, WIDTH half. Every grain lands on a fifth or an octave of the input, and a held note becomes a chord.

Stutter. A clock into TRIG, DENSITY off, POSITION a quarter, LENGTH a quarter, FADE fully left. Each beat replays a hard-edged fragment from a moment ago.

Backwards rain. REVERSE fully right, DENSITY half, SPRAY fully right, POSITION half, LENGTH three quarters, FADE fully right. Phrases come back reversed, scattered through the last second.

Frozen field. Play a phrase, press FREEZE, then raise DENSITY and SPRAY with POSITION at half. The grains pick through the frozen sound, turning round at its end, while you play over them. A slow LFO into POSITION's CV sweeps them through it.

Grain clock. DENSITY at the centre and START into a drum or an envelope: it fires with each grain, so the drum plays in time with the cloud.