Algorithmic Orchestration

April 9, 2026 · View on GitHub

Scoring music for a virtual orchestra via TidalCycles live coding. This document is the operational guide for the Algorithmic Orchestration principle — the paradigm of abstracting musical elements into three concerns: harmony/contexts (the Harmonic Algorithm), form/constants (the Spectral Narrative), and interfaces/timbres (instrument functions, voice lines, articulations).

Signal Chain

Code → TidalCycles → SuperDirt → MIDI → Roland JV-1010 → orchestral music

JV-1010 Configuration (16 MIDI Channels)

Channel	Instrument	Type
1	Flute	Wind
2	Oboe	Wind
3	Clarinet	Wind
4	Bassoon	Wind
5	Horn	Brass
6	Trombone/Bass	Brass
7	Harp	Plucked
8	Timpani	Pitched perc
9	Bass Drum	Unpitched perc
10	subKick	MPC sub/kick
11	Tam-tam	Unpitched perc
12	Strings pizz	String artic
13	Strings spicc	String artic
14	Strings marc	String artic
15	Strings legg	String artic
16	Strings arco	String artic

Performance Architecture

Voice leading (cyclic DP) is expensive. With 16+ stacked arrange calls (full orchestral mode), naive per-frame recomputation causes TidalCycles "skip" messages.

The fix is a construction-time voicing cache: arrange and arrange' query kProg k once when the pattern is registered, pre-compute voicings for all unique progressions (~2–3 in a typical form), and store them in an association list. Per-frame lambdas do O(1) lookup instead of running the DP solver. Result: ~800 voice leading solves/second → 2–3 (once at construction).

Frame timespan is set to 1/30 (~33ms frames). At oLatency = 0.15 (150ms SuperDirt latency), timing resolution is dominated by output latency — 33ms frames give more than sufficient musical precision.

Two Separate Concerns

(-9, 9) register — pattern index trimming. A compositional parameter passed to arrange. Controls how many scale degrees above/below the input patterns can reach. This is the composer's domain.
clip — MIDI range enforcement. Filters events whose MIDI note falls outside the physical instrument range. Internal to each instrument function — invisible to the composer.

These are independent: (-9, 9) controls compositional range, clip prevents impossible notes from reaching hardware.

Parameter Convention: `d` Last

All orchestral blocks (and updated existing blocks) take d as the last parameter, enabling the $ d syntax:

,wind f r k       $ d 0.9
,tutti arco f r k $ d 0.9
,k909 f k         $ d 0.4

Where d = (* 1) in the launcher — a dynamics multiplier applied via $.

Unified Block Template

Every block (section or blend) has the same two-part structure:

{name} f k d = p "{name}" $ do
  let vl = voiceLines {_vl = "~"
        -- , soprano = "3"
        -- , alto    = "1"
        -- , tenor   = "2"
        -- , bass    = "0"
        }
  f
    $ stack [silence
        , instrument (ki_range) k vl voiceFunc Voice
        , ...
    ] |* vel d

Voice declaration (vl): voiceLines with optional overrides
Instrument stack: each line is an instrument with kinetics range, IK context, voice lines, voicing paradigm, voice assignment

Instrument Functions

Pitched (arrange + clip + octave)

Each instrument is a partial application of instrument range channel:

instrument :: (Int, Int) -> Int -> (Double, Double) -> IK -> VoiceLines -> VoiceFunction -> Voice -> ControlPattern

Pipeline: arrange → # ch → |+ oct → clip

flute    = instrument (-12, 26)  1   -- C3-D6  (MIDI 48-86)
oboe     = instrument ( -2, 33)  2   -- Bb3-A6 (MIDI 58-93)
clarinet = instrument (-22, 34)  3   -- D2-Bb6 (MIDI 38-94)
-- etc.

Unpitched (struct-based)

bassdrum pat = struct pat $ midinote 36 # ch 9 # sustain 0.05
tamtam   pat = struct pat $ midinote 31 # ch 11 # sustain 0.5

Instrument Catalogue

Pitched Instruments

Instrument	Ch	Tidal Range	MIDI Range	Pitch Range	Section
Flute	1	(-12, 26)	48–86	C3–D6	Wind
Oboe	2	(-2, 33)	58–93	Bb3–A6	Wind
Clarinet	3	(-22, 34)	38–94	D2–Bb6	Wind
Bassoon	4	(-28, 15)	32–75	Bb1–Eb5	Wind
Horn	5	(-29, 17)	31–77	B1–F5	Brass
Trombone	6	(-28, 17)	32–77	Bb1–F5	Brass
Bass Trombone	6	(-39, -5)	21–55	A0–G3	Brass
Harp	7	(-29, 42)	31–102	B1–F#7	Plucked
Timpani	8	(-22, 0)	38–60	D2–C4	Pitched perc
Violin 1	16	(-5, 45)	55–105	G3–A7	Strings (arco)
Violin 2	16	(-5, 45)	55–105	G3–A7	Strings (arco)
Viola	16	(-12, 28)	48–88	C3–E6	Strings (arco)
Cello	16	(-24, 24)	36–84	C2–C6	Strings (arco)
Contrabass	16	(-36, 0)	24–60	C1–C4	Strings (arco)

Tidal note 0 = MIDI 60 = middle C. Ranges are enforced by clip inside each instrument function.

Unpitched Percussion

Instrument	Ch	MIDI Note	Usage
Bass Drum	9	36 (C2)	`bassdrum pat`
Tam-tam	11	31 (G1)	`tamtam pat`

subKick (separate signal chain — `"thru"` device, not JV-1010)

Part	Ch	MIDI	Notes
Sub	10	36–47	C2–B2 (pitch class + 36, mapped from harmonic root)
Kick	10	48	C3 (fixed)
Silence	10	35	B1 (no sample)

String Articulations

Strings default to arco (ch 16). Override with #:

Articulation	Ch	Alias	Usage
Pizzicato	12	`pizz`	`# pizz` or `tutti pizz f k $ d 0.7`
Spiccato	13	`spicc`	`# spicc`
Marcato	14	`marc`	`# marc`
Legato	15	`legg`	`# legg`
Arco	16	`arco`	Default (same as string channel)

JV-1010 Pan Positions

Ch	Instrument	Pan
1	Flute	-10
2	Oboe	10
3	Clarinet	-15
4	Bassoon	15
5	Horns	-22
6	Trombones	18
7	Harp	-25
8	Timpani	-18
9	Bass drum	-6
10	subKick/MPC	0
11	Tam-tam	22
12–16	Strings	0

Target Ensemble

2 flutes (doubling piccolo), 2 oboes (doubling cor anglais), 2 clarinets, 2 bassoons, 2 horns, 2 trombones (doubling bass trombone), 1 timpanist, 1 percussionist, 1 harp, 8 vn1, 6 vn2, 4 va, 3 vc, 2 cb

For interactive range tests, see live/ORCHESTRAL_CATALOGUE.tidal.

Voice Line System

SATB defaults

voiceLines = VoiceLines
  { _vl  = "~"     -- structural placeholder
  , soprano = "3"     -- soprano: root 8va
  , alto    = "1"     -- alto: 2nd degree
  , tenor   = "2"     -- tenor: 3rd degree
  , bass    = "0"     -- bass: root
  }

Overriding voices

let vl = voiceLines {_vl = "~"
      , soprano = "[3 2]/4"
      -- , alto    = "1"      -- commented = use default
      -- , tenor   = "2"
      , bass    = "[0 1]/4"
      }

The _vl field enables comma-leading syntax (same principle as stack [silence, ...]).

Voice Octave Variants

Standard Italian musical terminology for register shifts:

Suffix	Offset	Meaning
(none)	0	Loco (as written)
`8va`	+1	Octave up
`15va`	+2	Two octaves up
`8vb`	-1	Octave down
`15vb`	-2	Two octaves down

Applied to any voice: Soprano8va, Tenor8vb, Bass15vb, etc.

The octave shift happens inside the instrument function (via |+ oct) before clip filters. No |- oct 1 noise in templates.

String Articulations

Channel routing with default arco:

pizz  = ch 12    -- pizzicato
spicc = ch 13    -- spiccato
marc  = ch 14    -- marcato
legg  = ch 15    -- legato
arco  = ch 16    -- arco (default)

Override with #:

, violin1 (0,1) flow Soprano r k vl # pizz

For tutti, the articulation is a parameter:

tutti arco f r k $ d 0.9
tutti pizz f r k $ d 0.7

Sections

Name	Instruments
`wind`	flute, oboe, clarinet, bassoon
`brss`	horn, trombone, basstrom
`strg`	violin1, violin2, viola, cello, contrabass
`perc`	timpani, harp, bassdrum, tamtam

Blends

Name	Character	Instruments
`chalumeau`	Dark warmth	clarinet, bassoon, horn
`pastorale`	Mid-register colour	flute, oboe, clarinet
`brillante`	Bright top (flute 8va at high k)	flute 8va, flute, oboe, clarinet
`maestoso`	Full winds + brass (climactic)	wind + horn, trombone
`tutti`	Full orchestra	strings + winds + brass + timpani

Groove — subKick

subKick is a separate signal chain — it does not use the JV-1010. It routes via the "thru" device on MIDI channel 10 to an MPC (or equivalent sampler).

Note Mapping

Part	MIDI Note	Range
Sub	36–47	C2–B2 (pitch class → MIDI, mapped from harmonic root)
Kick	48 (fixed)	C3
Silence (no sample)	35	B1

Sub pitches are normalised from the progression's harmonic root pitch class: pitch_class + 36. This places the sub register below all orchestral instruments, leaving MIDI 48+ free for anything else sharing the channel.

CC64 Sustain Mechanism

The sub voice uses MIDI CC64 (sustain pedal) to hold notes:

sustain 0.01 triggers a brief note-on (the sampler latches it)
segment 16 CC64=127 background keeps the sustain held (~1 event/frame at 30fps)
CC64=0 at maxDur or subOffPat boundaries releases the note

This mechanism is intentional and must not be changed.

Voicing Cache

Voicings are pre-computed once at construction time (not per TidalCycles frame). All unique progressions in kProg k are resolved upfront; the per-frame lambda does a lookup instead of running the voice function. This eliminates hundreds of redundant computations per second in full orchestral mode.

Usage

subk f k d = p "subKick"
  $ f
    $ subKick d k root (maxDur, subOnStr, subOffStr, kickStr)

root or fund — always returns the harmonic root regardless of inversion
Sub group gates at (0.1, 1), kick at (0.2, 1) via ki
maxDur < 1 triggers auto-off; maxDur >= 1 means manual-off only

Kinetics Layering

Per-instrument kinetics ranges create crescendo ordering:

tutti art f k d =
  ...
    -- Strings foundation (always)
    , violin1    (0, 1)   k vl flow Soprano    # art
    -- Winds enter at 0.2
    , flute      (0.2, 1) k vl flow Soprano
    -- Brass at 0.5
    , horn       (0.5, 1) k vl flow Soprano
    -- Percussion at peak
    , timpani    (0.8, 1) k vl grid Bass8vb

As kinetics rises from 0→1, instruments enter progressively.

Examples

Basic: wind section

,wind f k $ d 0.9

Custom voice lines

wind' f k d = p "wind" $ do
  let vl = voiceLines {_vl = "~"
        , soprano = "[3 2]/4"
        , bass    = "[0 1]/4"
        }
  f
    $ stack [silence
        , flute    (0,1) k vl flow Soprano
        , oboe     (0,1) k vl flow Alto
        , clarinet (0,1) k vl flow Tenor8vb
        , bassoon  (0,1) k vl flow Bass8vb
    ] |* vel d

Full orchestra with articulation switching

,tutti arco f k $ d 0.9    -- arco strings
,tutti pizz f k $ d 0.7    -- pizzicato strings

Combined launcher

do
  let
    f = (swingBy 0.04 2)
    d = (* 1)
    k = iK tempo form (warp "[1 2 3 4]/8")
  mapM_ id [hush, setbpm tempo
    ,wind f k       $ d 0.9
    ,strg f k       $ d 0.8
    ,brss f k       $ d 0.9
    ,perc f k       $ d 0.7
    ,subk f k       $ d 1
   ]