Alchemy Lab / Capicola
Capicola
Real-time Time Stretcher
A collab with Heavylight Industries
Time stretching, in real time! Capicola stretches audio out while staying aligned to the rhythm of the input. Give your signal a glitched-out character without missing a beat. Capicola turns audio into envelope followers and triggers that can either self-modulate or feed to the rest of your rack. It’s a dynamic audio effect and CV utility in a 12HP package.

Slice, stretch, shift, distort
A novel time stretching algorithm
At its core, Capicola is the hardware implementation of “Extrema Sampling,” a novel data compression algorithm that reduces uniformly sampled 48kHz audio into non-uniform “Keyframes” of local extrema (peaks and valleys of the signal). The “Quality” knob determines the level of data compression applied in a continuous, modulatable fashion. It’s not bitcrush, it’s not downsampling. It’s a tape-like degradation the likes of which exist literally nowhere else.
This non-uniform sampling scheme, not dissimilar from Keyframe Animation in Blender 3D, is the basis for Capicola’s novel approach to “Overlap Add” time stretching in which the spacing between keyframes informs the granular crossfade duration. This inherently preserves the beats and tones, leaving the user with a “Grain Size” macro control.
Capicola also offers a novel approach to nonlinear distortion, again enabled by the keyframe representation. The distortion is applied to the keyframes in the “sparse domain” before the final interpolation, resulting in a naturally alias-free distortion that requires no oversampling and can facilitate many wild nonlinearities with ease.
Performance features
Real time stretch, real time play
Each of Capicola’s main controls is fully modulatable from either the internal envelope followers or external CV, with dedicated attenuverters for each control. The envelope follower is an excellent source of “self” modulation, and easily leads to evolving, dynamic patches with a mind of their own.
The “Threshold” control allows the user to easily create “glitch fills” by temporarily disabling the beat snapping. The settings of stretch, pitch, and grain size lead to anything from ethereal washes of time-stretched sound to beat-synced looping segments.
The visual feedback engine of Alchemy Lab makes multiple pages of controls a pleasure to use rather than an exercise in memory. Capicola utilizes four color-coded pages to offer settings that are wide enough in scope to offer supreme flexibility but only when the user needs it. The main controls are knob-per-function on the main panel, and everything else acts in service of them.
Interactive manual
Play
Settings
Control
Performance Page
Primary
The six knobs you play. Depth for each lives on the Depth page, source on the Routing page.
Grain pitch, decoupled from time. A detent at noon snaps to true unity.
Playback rate of the keyframe grid: realtime at CCW, a true freeze at the stop — the grid stops rather than crawling. Triggers still re-anchor it while frozen.
Self-calibrating: events are kept at knob × running average of the detector's own envelope. The top of the knob mutes auto-triggering — only B2 or Trig In slices.
How much keyframe material a grain covers before the head is sliced on.
Analyzer keyframe threshold. CW is full fidelity; CCW drops keyframes for a sparse, crunchy reconstruction. Lower quality = longer buffer.
Loop gain. Wet output → sinc saturator → bandpass → back into the recorder, where it is re-sliced and re-pitched. Above unity is deliberately unstable. The tap sits before the mix blend, so Mix down does not starve it.
Left input. The two channels are detected and sliced independently.
Right input.
External slice trigger. Rising edge, always accepted — even at threshold mute.
External modulation source, routable to any Primary knob from the Routing page. The only bipolar source of the three.
Triggers a slice, same as pressing the slice button.
Input follower envelope, mirrored on the P5 pip.
Gate on the output follower's transients.
Output follower envelope, mirrored on the P6 pip.
Left output, post-mix.
Right output, post-mix.
Heavylight X Hermetic Modular
About Heavylight
Heavylight Industries started with a frustrated sampler user figuring out how to time stretch on a device that offered no such feature. The end result was the idea of non-uniform sampling: a novel, fast, keyframe-sampling compression and stretch algorithm.
Capicola is the first embodiment of this algorithm, but the "Keyframe" idea can power so much more: an endless CV recorder, a sampler, or maybe even an entirely new time-frequency representation for signals that will drive another dimension of audio possibilities. Only time will tell.
Matthew (Heavylight) and Luke (Hermetic), both residents of Cascadia, met by chance online. Hours after reaching out, the pair from the Pacific Northwest were hacking on the hardware prototype that was to become Capicola.
At a Glance
Specifications
- Format
- 3U Eurorack
- Width
- 12 HP
- Depth
- Skiff friendly
- Power +12 V
- <199 mA (LED-dependent)
- Power −12 V
- <50 mA
- Audio
- 48 kHz / 24-bit stereo
- CV jacks
- 6, field-programmable
- LEDs
- 102 RGB
- USB
- Front-facing USB-C
- Storage
- Micro SD
- Engine
- Keyframe time-stretch
- Pitch and time
- Fully decoupled
- Slicing
- Per-channel transient detection
- Modulation
- Envelope followers, per pot
- Feedback
- 0 to 2.0
- Parameter lock
- Every pot
- Presets
- 16 slots
Open Platform
Use Any Alchemy Lab Firmware
Capicola is one firmware among many on the open Alchemy Lab platform. The hardware is field-programmable down to the silicon: load Echoa or Spagyros, build your own voice, or contribute back to the SDK. Capicola itself is open source, built on the Alchemy SDK.
License
MIT
HAL
Open
Panel templates
Included
Language
C++








