Glossary

The words of music theory, each defined in one plain sentence and explained with real notes.

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Arpeggio: An arpeggio is a chord whose notes are played one after another instead of all at once, usually rising from the lowest note to the highest or falling back down.

Cadence: A cadence is the chord progression that ends a musical phrase, and it tells the listener whether the music has finished or will go on.

Dominant: The dominant is the fifth degree of a scale, and the chord built on it (V), whose pull back to the tonic drives most endings in tonal music.

Enharmonic: Enharmonic describes two notes, intervals or keys that sound identical on a piano or guitar but are written with different names, such as C♯ and D♭.

Interval: An interval is the distance in pitch between two notes, named by a number that counts letter names, such as a third or a fifth, and a quality that fixes its exact size in semitones.
Inversion: An inversion is a chord played with a note other than its root as the lowest note, so the chord keeps its name but changes its bass and its shape.

Key signature: A key signature is the group of sharps or flats written after the clef at the start of every staff, telling you which notes are raised or lowered throughout the piece.

Leading tone: The leading tone is the note one semitone below the tonic, the seventh degree of the major scale, and its pull up into the tonic is what makes the dominant chord want to resolve.

Modulation: Modulation is a change of key within a piece of music, where a new note takes over as the tonic and a cadence in the new key confirms it.

Octave: An octave is the interval between two notes twelve semitones apart, such as one C and the next C up, where the higher note vibrates at exactly twice the frequency of the lower.

Relative minor: The relative minor of a major key is the minor key that uses exactly the same notes and key signature, with its tonic three semitones below the major key's tonic.

Scale degree: A scale degree is the position of a note in a scale, numbered from the tonic as 1, so that the same number names the same role in every key.
Semitone: A semitone, also called a half step, is the smallest interval in Western music, the distance from one note to the very next one, such as E to F or C to C♯.
Seventh chord: A seventh chord is a triad with a fourth note added a seventh above the root, as in G7 (G–B–D–F) or Cmaj7 (C–E–G–B).
Subdominant: The subdominant is the fourth degree of a scale, and the chord built on it (IV), which moves away from the tonic without pulling back towards it.
Syncopation: Syncopation is rhythm that places the accent where the beat does not lead you to expect it, on a weak beat or between beats, often holding that note through the next strong beat.

Time signature: A time signature is the pair of stacked numbers at the start of a piece that says how each bar is filled: the bottom number names a note value, and the top number says how many of them fit in one bar.
Tonic: The tonic is the first degree of a scale and the note a piece of music treats as home, the one a phrase can stop on and sound finished.
Triad: A triad is a chord of three notes stacked in thirds: a root, the third above it and the fifth above it.
Tritone: A tritone is the interval of six semitones, or three whole tones, which divides the octave exactly in half and is spelled as either an augmented fourth or a diminished fifth.