Music glossary

A concise, plain-English word-list of the music vocabulary that comes up as we build the music features — written for a software developer, with a programmer's analogy where it helps. Want the same ideas you can hear and click instead? Start with the interactive primer.

Prefer to read it beside the code? The fuller developer version — with every "why it bit us" note — lives in the repo at learn/music/GLOSSARY.md, next to tools/MUSIC_ENCODING.md.

The page Rhythm Performance Forms & eras Instruments Music ↔ code

1The page — how music is written down

Staff / stave (pl. staves): The five horizontal lines notes sit on. Graph paper for pitch: higher on the staff = higher sound.
Ledger line: A short extra line for a note above or below the five — the axis drawn a little further for one note.
Clef: The symbol at the far left that fixes which line means which pitch — the origin of the pitch axis. Treble clef = high (violin, right hand); bass clef = low (cello, left hand).
Grand staff: Two staves (treble + bass) joined by a brace, read together — how piano is written. ABC can't express this, so piano scores use MusicXML, which Verovio renders as two staves natively.
Pitch · octave · semitone: How high a note is, named A–G (then repeating). An octave is letter → same letter higher (+12 semitones). A semitone is the smallest step — any piano key to the very next one. Middle C = MIDI 60, everyone's landmark.
Accidental — sharp ♯ · flat ♭ · natural ♮: A symbol nudging a note ±1 semitone (or cancelling back). It lasts to the end of the bar, then resets — scoped state, not a per-note flag. Verovio derives MIDI pitch from the displayed accidental, not from MusicXML <alter> — get it wrong and the note plays a semitone off.
Key signature: A group of sharps or flats printed once at the start that applies by default all the way through; individual notes can still override.
Circle of fifths · "fifths": The keys form a ring; each step adds one sharp or removes one flat. So a key encodes as a single signed integer: 0 = C, +1…+7 sharps, −1…−7 flats. In our code that number is literally fifths.
Time signature · bar · beat: The stacked numbers say beats-per-bar (top) and which note is one beat (bottom). A bar (or measure) is one chunk between barlines; the beat is the steady pulse.

2Rhythm — how long things last

Note	Length (in 4/4)
whole	4 beats
half	2 beats
quarter	1 beat
eighth	½ beat
sixteenth	¼ beat

Dotted note: A dot adds half the note's value again (dotted quarter = 1½ beats).
Rest: A silence of a given length. Notation fills every beat, so gaps are explicit rests, never just absence.
Tie: A curve joining two notes of the same pitch into one longer sound — duration concatenation. Used to carry a note across a barline. In Verovio's ABC, a tie inside a chord bracket breaks the chord apart — so we only tie single→single, same pitch.
Slur: A curve that looks like a tie but isn't: it joins notes of different pitches, meaning "play smoothly" (legato). Changes articulation, not duration.
Tuplet · triplet: A group that doesn't divide evenly by two. The common one, a triplet, is three notes in the time of two — a non-power-of-two subdivision. Grids are powers of two, so triplets don't land on them; the Moonlight Sonata (all triplets) needs real tuplet support (3:2).
Anacrusis / pickup: One or more notes before the first full bar; the opening bar is short by exactly that much.
Chord · voice · polyphony: A chord is notes at the same instant (one onset, many pitches). A voice is one independent line within a staff; several at once is polyphony (a single line is monophonic).
Double stop: A string player bowing two strings at once to sound a chord.
Ornaments — trill · mordent · grace note: Little flourishes: a fast wobble to the note above (trill), a single quick flick (mordent), a tiny crushed-in note before the main one (grace). A notation program renders these as a cloud of very short notes ("note dust") that no clean grid can quantize — why some pieces are deferred.

3Performance — how it's played

Tempo: The speed, in BPM (beats per minute).
Dynamics · velocity: How loud: p (soft) … f (loud), plus crescendo/diminuendo. In MIDI this is velocity (0–127) — how hard a note is struck.
Articulation — legato · staccato: Legato = smooth, connected (what a slur asks). Staccato = short, detached, clipped with air between.
Phrase: A musical "sentence" — a run of notes shaped and breathing as a unit; players shape dynamics and timing per phrase.
Rubato: Flexible, expressive tempo — pushing and relaxing rather than strict clockwork.
Agogic: Emphasis by timing — leaning on a note by holding it a hair longer, instead of louder.
Vibrato: The small, fast pitch-wobble a string player adds with the hand.
Bowing · pedal · voicing: Bowing: which way the bow moves and which notes fall in one stroke (a slur = one bow). Pedal: the piano's sustain, letting notes ring on. Voicing: balancing a chord so the melody sings above the rest.
Solo vs tutti: One player alone vs everyone together — our ensemble-mode toggle.

4Forms, eras & catalogue numbers

Movement: A self-contained section of a larger work, with its own tempo and character — like a track on an album. Our "complete piece" bar means a whole movement.
Sonata · sonatina · concerto · symphony: A multi-movement piece for one/two instruments; a little one; a soloist vs orchestra; a large orchestral work.
String quartet · trio · serenade: Two violins + viola + cello; three players (piano trio = violin, cello, piano); a light multi-movement piece. Quartet parts feed our ensemble mode.
Short forms: Prelude (short opener), suite/partita (a set of dances — gavotte, minuet, sarabande, gigue), rondo (recurring refrain, A B A C A), nocturne (lyrical night-piece), étude (study), impromptu / bagatelle / intermezzo / caprice (short character pieces), gymnopédie / gnossienne (Satie's invented titles), canzonetta (little song), variations (a theme restated with changes).
Lied / Lieder · aria: German art song(s) for voice and piano (Schubert); a solo song from opera. Our string "arrangements" often borrow a Lied's melody (an octave shift).
The eras: Baroque (~1600–1750) · Classical (~1750–1820) · Romantic (~1820–1900) · Impressionist & Modern (~1890–1940).
Catalogue numbers: Stable IDs, like primary keys: Op. (opus), BWV (Bach), K. (Mozart / Köchel), Hob. (Haydn / Hoboken), D. (Schubert / Deutsch), RV (Vivaldi), G. (Boccherini / Gérard).

5Instruments & keyboards

Violin · viola · cello: The string family, high to low; bowed, or plucked (pizzicato).
Harpsichord · fortepiano · piano: Baroque keyboard that plucks a string (no touch dynamics); the early hammered piano ("loud-soft"); the modern piano. Clavier = a generic keyboard (Bach's Well-Tempered Clavier).

6Music ↔ code — our formats & tools

MIDI: Not audio — a list of events ("note 60 on at tick 0, velocity 80; off at 480"). A performance as data.
Tick · PPQ · onset: MIDI's clock is in ticks; PPQ = ticks per quarter-note (its resolution). An onset is a note-on time — what we align and compare on.
Quantize / grid: Snapping loosely-timed events onto a regular grid — and why triplets & ornaments are hard (they don't sit on it).
ABC: Compact text for a single-staff melody. Human-writable, great for cello/violin; no grand staff.
MusicXML: Verbose XML that handles grand staff, multiple voices and tuplets — our piano pipeline generates it.
Verovio · SVG · timemap: The engraving engine that reads ABC/MusicXML and renders SVG (the printed page) + MIDI (the sound) + a timemap — the table mapping each note's SVG id to its sounding time. The timemap is the join key that lets the score follow along.
Transpose · octave shift: Add a constant to every pitch (a vector add); ±12 is an octave — how our arrangements move a melody between instruments.

Spotted a term we use that isn't here, or an explanation a cellist would wince at? It's meant to be corrected and to grow — the source is learn/music/GLOSSARY.md.