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Add noon introduction article with piano roll visuals
- Introduces noon's core model, building blocks, and harmonic layer system - 6 piano roll diagrams illustrating chromatic/diatonic/structural/tonic steps, scale comparisons, structure comparisons, chord progressions, and layer mixing - Images generated from evaluated noon expressions with color-coded harmonic layers
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‎site/db.edn‎

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:url "https://hyperphor.com"
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:affiliation [:scicloj]
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:links [{:icon "github" :href "https://github.com/mtravers"}
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{:icon "mastodon" :text "Mastodon" :href "https://mastodon.social/@mtraven23"}
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]}
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]
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{:icon "mastodon" :text "Mastodon" :href "https://mastodon.social/@mtraven23"}]}
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{:id :pbaille
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:name "Pierre Baille"
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:image "https://avatars.githubusercontent.com/u/4739483"
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:url "https://github.com/pbaille"
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:links []}]
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:affiliation
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[{:id :clojure.core

‎src/music/noon_introduction.clj‎

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^{:kindly/hide-code true
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:clay {:title "Noon — Composing Music with Clojure"
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:quarto {:author :pbaille
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:description "An introduction to noon, a Clojure library for composing MIDI music using layered harmonic abstractions."
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:type :post
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:date "2026-02-10"
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:category :music
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:tags [:music :harmony :functional-programming :midi]
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:image "noon_introduction/steps.png"}}}
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(ns music.noon-introduction)
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;; ## What is Noon?
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;;
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;; [Noon](https://github.com/pbaille/noon) is a Clojure library for composing and playing MIDI music.
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;; The name comes from French — "noon" translates to "MIDI."
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;;
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;; The motivation is simple: digital audio workstations (DAWs) are powerful but slow.
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;; The feedback loop — click, drag, listen, repeat — doesn't match how musicians actually think about music.
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;; Musicians think in terms of scales, intervals, chord progressions, melodic contour.
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;; Noon tries to bring that level of abstraction into code.
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;; ## The Core Model
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;;
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;; A noon score is a set of event maps. That's it.
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;; Each event represents a MIDI note with properties like position, duration, velocity, and pitch:
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;;
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;;```clj
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;; noon.events/DEFAULT_EVENT
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;; ;; => {:position 0, :duration 1, :channel 0, :track 0,
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;; ;; :velocity 80, :pitch {...}, :voice 0, :patch [0 4]}
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;;```
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;;
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;; A fresh score contains a single event — middle C:
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;;
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;;```clj
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;; (score)
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;; ;; => #{{:position 0, :duration 1, ...}}
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;;```
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;;
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;; Everything in noon is a **transformation** — a function from score to score.
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;; You build music by composing transformations:
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;;
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;;```clj
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;; (play dur2 (tup s0 s1 s2 s3))
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;;```
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;;
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;; This plays an ascending arpeggio at double duration.
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;; `dur2` doubles the duration, `tup` splits it into equal parts,
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;; and `s0` through `s3` are structural intervals (more on those soon).
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;; ## Building Blocks
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;;
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;; Three core functions handle most of the composition:
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;;
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;; **`lin`** — concatenate transformations in sequence (a melody):
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;;
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;;```clj
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;; (play (lin C0 E0 G0 B0))
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;;```
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;;
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;; **`par`** — stack transformations simultaneously (a chord):
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;;
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;;```clj
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;; (play (par C0 Eb0 G0)) ; C minor chord
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;;```
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;;
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;; **`tup`** — like `lin`, but fitted to the current duration (a tuplet):
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;;
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;;```clj
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;; (play (tup c0 c3 c7 c10)) ; four notes in the space of one
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;;```
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;;
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;; These compose freely. A chord progression with arpeggios:
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;;
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;;```clj
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;; (play (lin I IV V I)
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;; (each (tup s0 s1 s2)))
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;;```
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;;
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;; And transformations can be chained using vectors:
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;;
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;;```clj
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;; (play [dur:2 (lin C0 E0 G0)])
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;;```
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;;
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;; A few more useful combinators:
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;;
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;; - `rep` — repeat a transformation accumulating results: `(rep 8 d1)` plays 8 ascending scale steps
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;; - `dup` — duplicate a score n times: `(dup 4)` repeats 4 times
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;; - `each` — apply a transformation to every event individually
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;; - `chans` — like `par` but on separate MIDI channels (for different instruments)
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;;
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;;```clj
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;; (play
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;; (chans
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;; [(patch :ocarina) (tup s0 s1 s2 s3) (rep 4 s1)]
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;; [(patch :vibraphone) vel3 (par s0 s1 s2)]
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;; [(patch :acoustic-bass) o1-])
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;; (dup 4))
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;;```
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;; ## How Musicians Think About Pitch
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;;
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;; Before diving into noon's harmonic system, let's consider how musicians actually think about notes.
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;;
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;; When a jazz musician sees a G7 chord symbol, they don't think "play MIDI notes 55, 59, 62, 65."
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;; They think: "root, third, fifth, seventh — in G mixolydian."
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;; If the chord changes to Gm7, they adjust their mental framework — same structure, different scale.
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;; The *relationships* between notes matter more than the notes themselves.
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;;
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;; This is a crucial distinction. Most music software works at the lowest level — absolute pitches, raw MIDI numbers.
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;; But musicians navigate a hierarchy of abstractions:
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;;
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;; - "Go up a semitone" — **chromatic** thinking
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;; - "Go to the next note in the scale" — **diatonic** thinking
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;; - "Go to the next chord tone" — **structural** thinking
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;; - "Go to the next octave" or "change the key" — **tonic** thinking
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;;
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;; Noon encodes this hierarchy directly.
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;; ## The Four Layers
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;;
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;; Noon's harmonic system is built on four layers, each one selecting from the layer below:
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;;
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;; **1. Chromatic** — the 12 semitones of an octave: `[0 1 2 3 4 5 6 7 8 9 10 11]`
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;;
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;; This is the raw material — every possible note.
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;;
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;; **2. Diatonic** — a selection of the chromatic layer forming a scale: `[0 2 4 5 7 9 11]`
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;;
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;; This is the major scale — 7 of the 12 chromatic notes. Change this and you're in a different scale (dorian, melodic minor, etc.).
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;;
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;; **3. Structural** — a selection of the diatonic layer forming a chord: `[0 2 4]`
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;;
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;; This picks the 1st, 3rd, and 5th degrees of the scale — a triad. Change this and you get a different chord shape (tetrad, sus4, etc.).
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;;
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;; **4. Tonic** — the root: `[0]`
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;;
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;; The single reference point everything is built from.
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;;
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;; Each event in a noon score carries this full context under its `:pitch` key:
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;;
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;;```clj
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;; (:pitch noon.events/DEFAULT_EVENT)
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;; ;; => {:scale [0 2 4 5 7 9 11] ; C major
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;; ;; :structure [0 2 4] ; triad
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;; ;; :origin {:d 35, :c 60} ; middle C
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;; ;; :position {:t 0, :s 0, :d 0, :c 0}}
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;;```
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;;
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;; The `:position` map holds an offset at each layer.
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;; This is where the note actually *is* within the harmonic context.
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;; ## Steps
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;;
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;; Each layer has a corresponding **step** operation.
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;; A step moves you to the next position *on that layer*:
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;;
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;;```clj
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;; (play (tup c0 c1 c2 c3 c4 c5 c6)) ; chromatic: semitone by semitone
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;; (play (tup d0 d1 d2 d3 d4 d5 d6)) ; diatonic: scale degree by degree
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;; (play (tup s0 s1 s2 s3)) ; structural: chord tone by chord tone
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;; (play (tup t0 t1 t2)) ; tonic: octave by octave
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;;```
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;; ![The four step types — chromatic, diatonic, structural, and tonic — each walking up from C4. Note how the same ascending pattern selects different notes depending on the layer. Colors indicate each note's role: tonic (dark blue), structural (medium blue), diatonic (light blue), chromatic (grey).](noon_introduction/steps.png)
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;; The chromatic run gives you all 7 semitones.
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;; The diatonic run gives you the major scale.
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;; The structural run gives you the arpeggio.
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;; The tonic run gives you octaves.
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;; Same syntax, different musical meaning — determined by the layer.
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;;
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;; Here's the key insight: **steps are always relative to the current harmonic context**.
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;; When you change the scale or structure, the same step operations produce different notes:
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;;
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;;```clj
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;; ;; Major scale
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;; (play dur:4 (lin d0 d1 d2 d3 d4 d5 d6 d7))
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;;
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;; ;; Dorian scale — same code, different result
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;; (play dur:4 (scale :dorian) (lin d0 d1 d2 d3 d4 d5 d6 d7))
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;;
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;; ;; Hungarian scale
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;; (play dur:4 (scale :hungarian) (lin d0 d1 d2 d3 d4 d5 d6 d7))
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;;```
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;; ![Same diatonic steps, three different scales. The code is identical — only the scale context changes. Notice how the intervals between notes shift while the structure remains.](noon_introduction/scales.png)
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;; The same goes for structural steps:
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;;
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;;```clj
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;; ;; Triad arpeggio
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;; (play (tup s0 s1 s2 s3))
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;;
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;; ;; Tetrad arpeggio — same code, richer chord
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;; (play (structure :tetrad) (tup s0 s1 s2 s3))
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;;```
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;; ![Triad vs tetrad: the same structural steps produce C-E-G-C with a triad structure, but C-E-G-B when the structure is set to tetrad — the seventh appears automatically.](noon_introduction/structures.png)
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;; ## Changing the Context
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;;
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;; Several functions let you reshape the harmonic context:
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;;
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;; **`scale`** — change the scale:
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;;
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;;```clj
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;; (play (scale :melodic-minor) (rup 8 d1))
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;;```
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;;
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;; **`structure`** — change the chord structure:
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;;
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;;```clj
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;; (play (structure :tetrad) (tup s0 s1 s2 s3))
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;;```
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;;
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;; **`root`** — change the tonal center:
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;;
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;;```clj
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;; (play (root :Eb) (tup s0 s1 s2))
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;;```
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;;
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;; **`degree`** — move to a scale degree (mode change):
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;;
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;;```clj
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;; (play (lin I IV V I) (each (tup s0 s1 s2)))
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;;```
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;; ![A I-IV-V-I chord progression, each chord arpeggiated. Dashed lines mark where the harmonic context changes — the same arpeggio pattern adapts to each degree.](noon_introduction/progression.png)
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;; Here `I`, `IV`, `V` are degree changes — they shift the harmonic context
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;; so that structural steps target the chord tones of each degree.
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;; The `each` function applies the arpeggio pattern to every chord individually.
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;; ## Mixing Layers
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;;
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;; The real power emerges when you mix layers.
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;; Since each event carries the full context, you can navigate between layers freely:
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;;
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;;```clj
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;; ;; Structural arpeggio with diatonic passing tones
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;; (play dur:2
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;; (tup s0 s1 s2 s3)
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;; (each (tup d1 d1- d0)))
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;;```
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;; ![Mixing layers: structural chord tones (medium blue) decorated with diatonic neighbor notes (light blue). The structural steps define the skeleton; the diatonic steps fill in the passing tones.](noon_introduction/mixing.png)
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;; This creates a chord arpeggio (`s0 s1 s2 s3`) then decorates each chord tone
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;; with upper and lower neighbor scale notes (`d1 d1- d0`).
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;; The diatonic steps know which scale they're in;
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;; the structural steps know which chord they're targeting.
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;; They coexist naturally.
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;;
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;; An arpeggiated chord progression in harmonic minor:
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;;
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;;```clj
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;; (play (scale :harmonic-minor)
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;; (lin I IV VII I)
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;; (each (tup s0 s1 s2)))
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;;```
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;; ![Harmonic minor progression: I-IV-VII-I with arpeggiated chords. Notice the characteristic G♯ (raised 7th degree) appearing in the VII chord.](noon_introduction/harmonic-minor.png)
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;; ## Why This Matters
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;;
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;; In most music programming systems, if you want a chord arpeggio, you specify exact intervals:
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;; "0, 4, 7 semitones" for major, "0, 3, 7" for minor.
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;; If you change the key or the chord quality, you rewrite the intervals.
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;;
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;; In noon, `(tup s0 s1 s2)` means "play the first three chord tones" regardless of context.
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;; Put it in C major and you get C-E-G.
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;; Put it in D dorian and you get D-F-A.
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;; Change to a tetrad structure and `s3` appears as the seventh.
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;; The code expresses the musical *intent* — "arpeggiate the chord" — and the harmonic context handles the rest.
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;;
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;; This mirrors how musicians think.
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;; A jazz musician doesn't memorize separate fingerings for every chord in every key.
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;; They learn *patterns* — "1-3-5", "approach from below", "enclosure" — and apply them across contexts.
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;; Noon works the same way.
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;;
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;; ---
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;;
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;; Noon is open source — [github.com/pbaille/noon](https://github.com/pbaille/noon).
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;; There's also an [online playground](https://pbaille.github.io/noon/) where you can try it in the browser.

‎src/music/noon_introduction/harmonic-minor.png‎

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‎src/music/noon_introduction/mixing.png‎

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‎src/music/noon_introduction/progression.png‎

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‎src/music/noon_introduction/scales.png‎

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‎src/music/noon_introduction/steps.png‎

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‎src/music/noon_introduction/structures.png‎

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