Playback engine 14 of 15
Stochastic
Continuously deform a recording with evolving timing and amplitude shapes. Each note follows its own bounded random walks while the original stereo sample supplies every sound.
Good for: metallic tearing, unstable reeds, growling voices, elastic machinery and dense changing textures. Start with a sustained recording so its changing shape is easy to hear.
Pages and navigation
Choose Stochastic with ALG on the Engine page. The waveform header abbreviates it as STOCH; Engine List entries show STOC. Menu opens its parameter pages. Stochastic has one unique page, plus the shared Engine, Pads & Scale, Amp Envelope and Stack Path pages. Quad omits Stack Path.
Stochastic — every parameter
| Knob | Display | Range | What it controls |
|---|---|---|---|
| 1 | SIZE | 1–64 cycles | Fragment size chooses how many analyzed cycles make up a local source fragment. Smaller groups give compact, rougher shapes; larger groups preserve more of the recording. Playback bounds fragments to about 0.75–350 ms of source audio. Before analysis is ready, or where there are too few crossings, each requested cycle contributes 5 ms to a windowed fallback. Large changes settle over several overlapping fragments. |
| 2 | AMUT | 0–100% | Amplitude mutation moves from local gain changes into polarity inversion and repeated reflected folding of the recorded waveform. The upper range deliberately changes its harmonic structure dramatically. Zero removes this deformation. It adds no oscillator, hiss or noise source. Character pressure raises this amount for the pressed note. |
| 3 | TMUT | 0–100% | Timing mutation stretches and compresses sixteen internal sections through an accumulated logarithmic time map. The upper range can concentrate much of the source into a short part of the fragment, producing tearing, stretched plateaus and sharp changes in timbre. Reading stays forward and continuous. Zero leaves the local time map straight. Total duration is normalized before DRFT. Waveform-view knob 7 is a shortcut to this control. |
| 4 | EVOL | Hold / Hz / CYC | Evolution rate requests walk steps in Hz. The dial follows a logarithmic curve for precise slow rates and quick access to fast mutation. Its maximum reads CYC and advances the walk once per complete fragment cycle. LSTN can slow both clocks as capture builds. New shapes enter through silent overlap boundaries; free-rate work is limited to four steps per incoming fragment, so long fragments and low notes can cap the effective rate. Hold stops the walks while playback continues. Each new note starts with an independent shape. Set AMUT, TMUT and DRFT to zero to remove their deformations. |
| 5 | MEM | 0–100% | Walk memory controls persistence in each walk’s direction. Higher values carry previous movement farther before it changes direction. The resulting gain and local-stretch histories accumulate between passes; low PULL allows them to move far from the source shape. Lower MEM gives less persistent movement. It does not store or recall a recording. |
| 6 | PULL / CAPT | 0–100% | Outside LSTN, source attraction draws the accumulated timing and gain histories back toward their original neutral shape. Low values allow larger excursions; high values keep the sound closer to its source. In LSTN this knob becomes CAPT, the strength of internal feedback that restrains mutation and evolution. PULL and CAPT keep separate saved values. LSTN retains the found shape instead of pulling it toward neutral. AMUT and TMUT at zero remove their deformations completely. |
| 7 | LAW | SMTH / FLAT / WIDE / LSTN | Walk law chooses centrally weighted, uniform, or sparse wider steps. WIDE gives more occasional large excursions. LSTN uses WIDE steps with a listener that slows and restrains their movement. All four use bounded movement; changing LAW preserves the current walk. |
| 8 | DRFT | 0–100% | Period drift allows slow wandering of the overall fragment duration and pitch, up to approximately half an octave in either direction. Zero removes this random period variation while TMUT can continue changing the internal shape. The recording’s own pitch contour remains audible. |
Listener capture
Set LAW to LSTN and turn CAPT on knob 6. The part’s internal note signal governs how firmly each Stochastic note settles into its current deformation. Capture builds in about 140 ms and releases more slowly, over about 2.2 seconds. Higher CAPT restrains amplitude/timing mutation, walk momentum and evolution rate more strongly. A small evolution floor keeps the shape alive; EVOL Hold remains the deliberate full stop. CAPT at zero leaves WIDE movement with no source attraction.
The listener uses stereo energy from the part’s ordinary note voices after their amplitude envelopes and before output level, part level and effects. Each note has its own capture state and relative contribution; other parts, microphone monitoring, sample preview, Rolls and effects returns do not feed it. In an Engine List, other ordinary notes in the same part can contribute to its internal signal. Effects and master-volume changes therefore do not change capture. It responds to signal activity, rather than judging musical quality.
Capture does not directly turn down the sound, retune keyboard notes, stop source travel or pause stack scanning. Deformation can change perceived loudness as it settles. Hold the source, latch notes and hold stack scan independently. LAW and CAPT are saved and recordable with performances; the live listening state starts fresh for a new note.
Hold a fragment and transform it
On the Stochastic parameter page, click the main encoder to hold the part’s current source position. The footer changes to SRC HELD CLICK: RUN. Walks, folding, note pitch and stack scanning continue while fragments are taken from that point. Click again to resume source travel from the held point. Existing readers finish their overlap, so the change can take part of a fragment to settle.
The position comes from the most recently played active Stochastic note in that part, favoring held notes. With no active Stochastic note, it uses Position. New notes reuse the held source position and start independent deformations. Position and Field still bound the usable area; cues can move the held point. Source hold and its position are saved with clips and captured as discrete performance events.
Independent holds: Shift + note latches a note; set Pads & Scale HOLD to MAN for indefinite latching. Main-encoder click on this page holds source travel. Loop holds stack scanning. EVOL at Hold stops deformation evolution. These controls can be combined.
Playing and lanes
Keyboard notes transpose the sampled fragments relative to Root. Speed controls travel through the recording independently; Position and Field select its usable region. The waveform cursor shows that scanning position rather than every overlapping fragment. Extreme note ranges are bounded to keep processing and reading rates finite.
Stack Start, Scan Rate, stack paths, and Loop’s scan hold work as on the other scanning engines. The timing map is shared between left and right channels, preserving their relationship. Each note retains its own walk through lane changes. Single has eight source voices, Split and Shared Dual four per part, and Quad two per part. Stochastic can also be an entry in an Engine List.
Two overlapping readers blend fragment changes. Live edits take effect through the incoming fragments; long fragments and low notes respond more gradually. Prepared crossing maps are built in the background. A fallback keeps playback available while they are pending. Silent or empty recordings produce no new sound. The source analysis also prepares stereo low-pass levels for fast time warps. Reflected folding uses antiderivative anti-aliasing, with both channels sharing timing and filtering. Preparation enters through a smooth blend. These safeguards reduce unwanted digital edges while retaining intentionally rough spectra. Join is shared with the other engines; Stochastic uses its own complementary overlap windows.
Starting points
For a self-settling texture, select LAW LSTN, start CAPT at 65% and raise it toward 100% for stronger restraint. AMUT and TMUT still set the available depth. New programs start at SIZE 2, AMUT 65%, TMUT 70%, EVOL 100 Hz, MEM 80%, PULL 10%, LAW WIDE and DRFT 0%. For the most drastic transformation, latch a note, click to hold its source, set AMUT and TMUT to 100%, MEM to 90%, PULL to zero and EVOL to CYC or a fast Hz rate. Small SIZE values give rapid evolution; larger values expose more of the original sample. Add DRFT for pitch wandering. For a gentler deformation, lower AMUT/TMUT to 10–25%, EVOL to 1–4 Hz and raise PULL to 60–90%.
The two orders of random walk extend ideas from s3g-dsp’s Stochastic Encoder and Xenakis’s dynamic stochastic synthesis. Here those walks deform recorded PCM instead of generating breakpoint audio waveforms. It is a sample playback interpretation of those processes.
MIDI and saved performances
The original eight controls retain NRPN addresses 3200–3207 on part channels 5–8. LAW now spans 0–3; custom controllers must update their enum encoding. CAPT is the additional per-part NRPN 3210 (0–100%). PULL remains 3205 even when hidden. EVOL now spans 0–1024; the endpoint selects CYC. Source Hold is NRPN 3208 (Off/On); held position is 3209 (0–1). E16 ENG 1 follows these controls for each part. Move switches knob 6 between PULL and CAPT for each part. Source hold is controlled on Move or through its NRPN address. Parameter edits, engine choices and per-note entry assignments can be recorded and recalled with clips. See MIDI control for setup.