Theory dictionary

Every term in one honest sentence, the same plain-language definitions the Theory Aide extension shows as tooltips inside Ableton Live. Click any term for a fuller description and a link to where it is taught.

• bar A group of beats, most often four, marked by the heavier grid lines.
• beat The steady pulse under music, the thing your foot taps.
• borrowed A chord taken from the parallel major/minor for extra color.
• cent One hundredth of a semitone, the unit for measuring tiny differences in tuning.
• characteristic note The one note that separates a mode from plain major or minor, the note that makes it that mode.
• chord Several notes sounding together, heard as one object with a mood.
• circle of fifths The twelve keys arranged in a wheel so neighbors differ by one note. Distance on the circle is harmonic distance.
• consonance The smooth, settled quality of intervals whose waves fit together simply.
• contour The overall shape of a melody: where it rises, peaks, and falls.
• contrary motion Two voices moving in opposite directions. The most independent, strongest motion.
• density How many notes sound at once or in quick succession. How full it feels.
• diatonic Belonging to the key: built only from the scale's own notes.
• dissonance The rough, restless quality of intervals whose waves never settle.
• dominant The tension chord that wants to fall back to the tonic (the V).
• dorian A minor mode brightened by a natural sixth: the hopeful minor of modal jazz and funk.
• drone A note held or repeated under everything else, giving the ear a fixed home to measure against.
• equal temperament Tuning that splits the octave into twelve identical steps, so every key is equally playable and equally, slightly, out of tune.
• frequency How many times per second something vibrates. In sound, faster means higher.
• hertz The unit for frequency: one hertz is one back-and-forth per second.
• hidden fifth Both voices leap the same direction into a 5th, a softer parallel-5th.
• hidden octave Both voices leap the same direction into an octave.
• interval The distance between two notes, counted in semitones and heard as a flavor.
• just intonation Tuning built from pure small-number ratios: flawless in one key, unusable in the others.
• key The gravity field of a scale: one note is home, and every other note is heard by its distance from home.
• leading tone The note a semitone below home, which pulls strongly up to it.
• locrian The mode on the seventh degree, with a diminished home chord and no stable fifth, so it barely works as a key.
• lydian A major mode with a sharp fourth: floating and weightless, the wondrous major.
• melody A sequence of single notes heard as one continuous line with a shape.
• mixolydian A major mode with a flat seventh: the bluesy, rock dominant that will not fully resolve.
• mode A scale defined by which of its notes is treated as home; the same notes yield a different mode from each starting point.
• oblique motion One voice holds while the other moves.
• octave The distance between a note and the note vibrating twice as fast. They sound like the same note, higher.
• parallel fifths Two voices a 5th apart moving the same direction, the classic counterpoint no-no.
• parallel motion Two voices moving the same direction by the same interval.
• parallel octaves Two voices an octave apart moving together, collapsing two lines into one.
• pentatonic A five-note scale with no semitones, so nothing in it clashes or demands resolution.
• phrygian A minor mode with a flat second: dark and tense, the Spanish and metal sound.
• pitch How high or low a note sounds, set by its frequency.
• register How high or low the notes sit overall.
• relative key A major and minor key that share the exact same notes, differing only in which note is home (C major and A minor).
• roman numeral A chord named by its scale degree instead of its letter, so the name survives a key change.
• root The note a chord is built from and named after.
• scale A chosen set of notes defined by a pattern of steps, repeating every octave.
• secondary dominant A V chord aimed at a chord other than the tonic, briefly making it feel like home.
• semitone The smallest step on the piano roll: one row up or down. Twelve make an octave.
• similar motion Two voices moving the same direction by different amounts.
• subdominant Harmony that pulls away from home and sets up tension (the IV side).
• syncopation Accents landing off the strongest beats, giving a pushed, lively feel.
• tempo How fast the beats come, measured in beats per minute (BPM).
• tonic The home chord or note, where the music feels at rest.
• triad The basic three-note chord: a root, a third, and a fifth, stacked.
• voice One continuous musical line in a texture, whether or not anyone is singing.
• voice leading How each line moves note-to-note from one chord to the next.