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Pitch Logic

The Pitch Logic card determines what notes play. It combines a scale selection system (112+ scales) with a pitch pattern algorithm (10 methods) that decides how pitches are chosen from the scale. All pitch patterns are streaming — they maintain internal state and produce the next pitch in O(1) time.

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Pitch Pattern Algorithms

AlgorithmWhat It DoesLineage
SequentialAll pitches in the set must sound before any can repeat (with octave displacement allowed). Ensures chromatic completeness within each cycle. Each pattern parameter controls the spread of octave displacement.Schoenberg, twelve-tone technique (1923). Serial exhaustion — aggregate completion as structural principle. Extended here to any pitch set, not just the chromatic.
SpiralSpirals outward from a center pitch, alternating above and below in expanding intervals. Creates a widening melodic cone. The center pitch is configurable.Xenakis, arborescences — tree-like branching pitch structures (Evryali, 1973). Spiral motion as generative principle.
FibonacciNext pitch determined by Fibonacci interval sequence (1, 1, 2, 3, 5, 8, 13, 21 semitones). Direction reverses when pitch boundaries are reached. Pattern parameter scales the interval magnitudes.Fibonacci sequence. Bartók’s intervallic proportions. Lendvai’s golden section analyses of Bartók’s pitch structures.
RegisterSystematic traversal through octave registers — plays through all pitches in one octave before moving to the next. Traversal order varies from sequential to shuffled based on the pattern parameter.Messiaen’s modes of limited transposition — systematic register exploration. Registral stratification in Webern.
ProbabilisticWeighted probability transitions where closer intervals have higher probability. Pattern parameter (Leap) shifts the bias from stepwise motion toward large leaps.Xenakis, Markov chains in music (Analogique A, 1958). Hiller & Isaacson, Illiac Suite (1957) — first computer-generated composition using Markov chains.
Golden RatioDivides the pitch set at the golden ratio point (φ ≈ 0.618), creating two subsets. Alternates between subsets, cycling through each independently. Pattern parameter adjusts the split point.Golden section applied to pitch-space partitioning. Proportional subdivision as melodic generator.
BeatingConstructs a pitch set from the interference of two interval generators. All pitches satisfying (root + n×A + m×B) mod 12 are collected, producing combination-tone-derived scales. Pattern parameter adjusts the generating intervals.Grisey and Murail, spectral music (Partiels, 1975). Combination tones and resultant pitch sets from interval interference.
MirrorAlternates between original pitches and their inversion around a configurable axis pitch (2×axis − pitch). Creates palindromic pitch contours. Pattern parameter sets the axis.Serial inversion technique (Schoenberg, Webern). Symmetric pitch structures — Bartók’s axis of symmetry system.
PermutationSystematic reordering of the pitch set through circular rotations, retrograde, retrograde-inversion, or all transformations. Pattern parameter selects the variant.Combinatorial twelve-tone technique (Babbitt). Permutation groups applied to pitch ordering — exhaustive traversal of set transformations.
CorpusPitch transitions learned from MusicBERT analysis of 3.44 million MIDI files. Uses pitch-class transition matrices extracted from the pre-trained model. Context parameter biases toward ascending motion, stepwise motion, or large leaps. Falls back to Probabilistic behavior if no corpus data is loaded.MusicBERT (Zeng et al., 2021). Statistical learning of pitch transitions from large-scale musical corpora.

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Parameters

ParameterIDRangeDefaultDescription
Pitch SelectionpitchPatternType0–90Algorithm selection
Pitch Pattern ShapepitchPatternParam0.0–1.00.5Algorithm-specific control (see table below)
ScalescaleIndex0–1500Scale selection from library
Root Pitch ClasspitchClass0–110 (C)Root note (C, C#, D, … B)
Starting Octaveoctave−1–93Base octave for pitch set
Octave SpanoctaveSpan1–104Number of octaves to span
Custom Pitch ClassescustomPitchClasses0–40954095Bitmask for custom scale (bit 0=C through bit 11=B)

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Pattern Parameter Meanings

The pitchPatternParam slider controls different aspects depending on the active algorithm:
AlgorithmParameter LabelEffect
SequentialSpreadOctave displacement range
SpiralCenterCenter pitch position
FibonacciRangeInterval magnitude scaling
RegisterOrderSequential ↔ shuffled traversal
ProbabilisticLeapStepwise ↔ leaping bias
Golden RatioSplitSplit point adjustment
BeatingIntervalGenerating interval adjustment
MirrorAxisInversion axis position
PermutationVariantTransformation type selection
CorpusContextMotion bias (ascending / stepwise / leaping)

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Scale Library

PERF includes 112+ scales spanning:
  • Western modes — Major, Minor, Dorian, Phrygian, Lydian, Mixolydian, Locrian, Harmonic Minor, Melodic Minor
  • Pentatonic and blues — Major Pentatonic, Minor Pentatonic, Blues
  • Symmetric — Whole Tone, Chromatic, Diminished, Double Diminished
  • Japanese — Kumoi, Iwato, Hon-Kumoi-Joshi, Banshiki-Cho, Naka Zora, Noh, Kokin-Choshi, Shimo-Chidori, and more
  • Indian ragas — Yaman, Bhairavi, Todi, Marwa, Lalit, Hindole, Kafi, and more
  • Yusef Lateef’s Repository — Mono-quality triads, quartal formations, hetero-quality triads, mutated hexadic scales, intervallic mutations, and synthetic constructions
  • Ancient — Archaic Greek, Chinese Reform, Mongolian
  • Custom — User-defined pitch class set via bitmask
See Scale Reference for the complete list with descriptions.