Music Theory Glossary

These are the terms you will meet across our tools and articles. Don't just read them — follow the links and hear each idea for yourself.

Basics

Note name: The letters C, D, E and so on. "Do-re-mi" is the same set of notes with Italian-derived names (C = do, D = re). Our tools use the international letter names.
Octave: The same note name at a different height — a low C and a high C. Doubling the frequency takes you up exactly one octave.
Semitone and whole tone: A semitone is the distance between two adjacent keys on the keyboard, black keys included. Two semitones make a whole tone. Every scale is a recipe of these two distances.
Interval: The distance between two notes, named like "major 3rd" or "perfect 5th". Chords and melodies are all built from intervals. Hear it Interval calculator → What is an interval? →
Key: The home note and scale a song is built around, such as "C major". Once you know the key, you can predict most of the notes and chords the song will use. Hear it Key finder →
Scale: A set of notes arranged in order of pitch — the pool of "usable notes". The major scale is the most basic one, and the scale you choose shapes the whole mood of a piece. Hear it Scale dictionary →
Major and minor: Bright sound = major, dark sound = minor. Remarkably, the difference comes down mostly to one note: the 3rd, a semitone apart. Hear it What is a scale? →
Transposition: Shifting an entire song up or down to a different key — for example to match a singer's range or make a part easier to play. Hear it Transpose tool →

Chords

Chord: Several notes of different pitch sounding together. Three or more notes is the usual starting point. Hear it Chord finder →
Root: The foundation note of a chord — the letter at the front of the chord name (the C in Cm).
Triad: The most basic chord: root + 3rd + 5th. C, Dm, and Em are all triads.
Seventh chord: A triad plus a 7th — four notes, like Cmaj7 or G7. The sound instantly becomes richer and more grown-up.
Chord progression: Chords arranged in time. The sense of movement and emotion in a song comes largely from its progression. Hear it Progression player → What is a chord progression? →
Diatonic chords: The seven chords you can build using only the notes of the key's scale — the "safe list" of chords for that key, and the natural starting point for songwriting. Hear it Diatonic chord chart → What are diatonic chords? →
Degrees (Roman numerals): Writing chords as Roman numerals (I, IV, V…) instead of letter names. The same progression reads identically in every key, which makes patterns much easier to memorize.
Chord function (T, SD, D): A way of classifying what each chord does: tonic (T) = stable home, subdominant (SD) = movement and color, dominant (D) = tension that wants to resolve back to the tonic. Hear it Tonic, subdominant, dominant →
Cadence: A standard way of ending a phrase. The dominant-to-tonic resolution (G to C, for example) is the classic "this is the end" sound.
Voicing: How you stack and order the notes of a chord. The same C chord can sound open, tight, bright, or muddy depending on the voicing.
Tensions: Color notes — 9ths, 11ths, 13ths — added on top of a basic chord. Jazzy, sophisticated harmony usually comes from tensions. Hear it Melody note guide →
Borrowed chord: A chord borrowed temporarily from the parallel scale — like an Fm appearing in a C major song. A favorite trick for adding bittersweet color. Hear it What are borrowed chords? →
Secondary dominant: A temporary dominant aimed at a chord other than the tonic, creating a brief pull toward it. It adds forward momentum to a progression.

Scales and melody

Circle of fifths: The twelve keys arranged in a circle, a fifth apart. Neighboring keys share most of their notes, so key signatures and related keys become visible at a glance. Hear it Circle of fifths → What is the circle of fifths? →
Key signature: The set of sharps or flats at the start of a staff, telling you the key. The number of sharps and flats grows in circle-of-fifths order.
Mode: Seven different scales created from one set of notes by changing which note you start on. Modes give you moods that plain major and minor can't. Hear it Mode dictionary →
Pentatonic: A five-note scale. Almost any order of its notes sounds good, which makes it the perfect entry point for improvising and writing melodies.
Chord tones and scale tones: Chord tones are the notes of the chord currently playing (your melody's "landing spots"); scale tones are the rest of the key (the "paths between"). Using them deliberately is the core of melody writing. Hear it Melody note guide →

Rhythm

BPM (tempo): Beats per minute. At 120 BPM you get two beats every second; the bigger the number, the faster the song. Hear it Metronome → Tap tempo →
Time signature: How beats are grouped. 4/4 (four quarter-note beats per bar) is by far the most common; a waltz is 3/4.
Offbeat: The "and" between the counted beats: 1-and-2-and… Feeling the offbeat is the quickest way to make your rhythm steadier. Hear it Rhythm pattern dictionary →
Syncopation: Placing accents where you don't expect them — on weak beats or offbeats. That driving, groovy feel in pop and funk is mostly syncopation.