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MIR Capture

MIR Capture analyzes incoming MIDI notes in real time and builds a Performance Fingerprint — a multi-dimensional model of the playing style. The fingerprint then seeds RESERVOIR’s rhythm, pitch, perforation, and micro-timing engines, so generated output inherits characteristics of the captured performance while still being shaped by RESERVOIR’s algorithmic pipeline.

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How It Works

Capture is automatic. Route MIDI input to the track that hosts RESERVOIR and play. The engine status label in the bottom bar reflects the capture state:
LabelStateWhat’s happening
IdleNo MIDI received yetEngines run normally
Learning... N notes (X%)CapturingNote-ons are accumulating; confidence rises as more notes arrive
Seeded: <Key> (key fit X%)SeededFingerprint is computed; engines that support seeding are using it
Hover the status label for a multi-line tooltip with the full fingerprint breakdown (detected key, grid resolution, swing, density, phrase length, articulation profile, polyphony).

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State Machine

Idle → Capturing → Seeded
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The machine transitions:
  • Idle → Capturing — On the first incoming MIDI note-on
  • Capturing → Seeded — Once enough notes are captured for a stable fingerprint (~8 notes minimum, 30+ for reliable rhythm/groove)
  • Seeded → Idle — On a transport jump or region boundary (onPlayheadDiscontinuity); the next note-on restarts capture from scratch
There are no manual CAPTURE / STOP / APPLY buttons — the state advances automatically based on incoming MIDI and transport state.

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What Gets Analyzed

The Performance Fingerprint captures six dimensions:

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Pitch Model

  • Pitch-class transition matrices (PPM-Decay variable-order Markov), separate ascending and descending
  • Interval distribution — preference for stepwise motion vs leaps
  • Scale + root detection via Krumhansl-Schmuckler key correlation
  • Register histogram — which octave ranges are favored
  • Register slope — whether playing trends upward or downward

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Rhythm Model

  • IOI ratio transitions — inter-onset intervals quantized to 12 musical categories (PPM-Decay)
  • Mean density and variance
  • Tempo estimation — beat tracking via autocorrelation with perceptual weighting (80–160 BPM preferred)

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Groove Model

  • Per-grid-position deviations at 12 sub-beat positions
  • Per-position variance — how consistent the timing is at each position
  • Swing ratio — even-to-odd eighth-note timing ratio

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Phrase Model

  • Phrase boundaries detected via LBDM (Local Boundary Detection Model) over pitch, IOI, and rest streams
  • Mean phrase length in notes

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Articulation Model

  • Gate ratio — how long notes are held relative to the inter-onset interval
  • Dominant style — classified as Legato, Staccato, Accent, or Mixed
  • Style fractions — proportion of staccato, legato, and normal notes

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Velocity Model

  • Range and statistics — min, max, mean, variance
  • Velocity curve — envelope shape extractable for the Captured setting on velocityCurveShape

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Seeded Engines

When the fingerprint is active, four subsystems can draw on it:
  • Rhythm — PPM-Decay Markov trained on captured IOI ratios. The Density Min/Max range acts as a morph between the captured rhythm and the selected algorithmic engine.
  • Pitch — PPM-Decay Markov over captured pitch-class transitions, with directional submodels. The Pitch Shape parameter morphs between captured and algorithmic.
  • Perforation — Context-dependent rest insertion conditioned on note length and pitch direction. The Perforation amount morphs between captured rests and the selected method.
  • Micro-Timing — Set microTimingStyle to User Groove to apply the captured per-grid-position deviations and swing ratio.

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Preset Integration

The fingerprint is saved and restored with presets. Saving a preset while a fingerprint is active serializes the full fingerprint (matrices, distributions, models) as JSON inside the preset. Loading that preset restores the fingerprint and re-seeds the engines.

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Tips

  • Minimum viable capture: 8–10 notes produce a basic fingerprint. 30+ notes over 15+ seconds give reliable phrase and groove detection.
  • Consistent style: The analyzer reflects what it sees. Mixed playing produces averaged results.
  • Steady tempo: Best groove extraction comes from steady tempo input. The beat tracker prefers 80–160 BPM.
  • Re-capture freely: Triggering a transport jump (stop/seek) drops the current fingerprint and re-enters Idle; the next note-on starts a fresh capture.
MIR Capture requires incoming MIDI — from a controller routed through the DAW, or from MIDI clips on RESERVOIR’s track. The DAW must route MIDI input to the track that hosts RESERVOIR.