Note Names and Octaves
The basic system Western music uses to represent pitch β understanding note names (C D E F G A B) and the concept of the octave is the starting point of music theory. Note names are typically written using the letter system (C D E F G A B) in chord notation. An octave is the relationship between two notes of the same name whose frequency doubles β on a piano, it's the span between one white key and the next key with the same name.
Intervals
The distance between two notes β the most fundamental unit for understanding chords and melody. An interval is described by both a number (2nd, 3rd, etc., indicating how many scale steps apart) and a quality (major, minor, perfect, augmented, or diminished). The 3rd interval (major or minor) is especially important, since it's what determines whether a chord sounds bright or dark. For example, C to E is a major 3rd, and C to G is a perfect 5th.
Whole Steps and Half Steps
The smallest building blocks of a Western musical scale β the pattern of whole steps (two half steps) and half steps (the smallest interval) determines a scale's character. On a piano, the distance to the very next key (including black keys) is a half step, and two half steps make a whole step.
The Major Scale
A bright, stable-sounding scale built from a fixed pattern of whole and half steps: whole-whole-half-whole-whole-whole-half. This interval pattern stays exactly the same no matter which note you start on (the tonic). Example: C major scale: C-D-E-F-G-A-B-C.
The Minor Scale
A darker, more melancholic-sounding scale, with three main forms: natural minor, harmonic minor, and melodic minor. The natural minor uses the exact same notes as a major scale, just starting from a different note (its relative minor). The harmonic minor raises the 7th degree by a half step for a stronger sense of resolution in the dominant chord, and the melodic minor raises the 6th and 7th degrees when ascending for a smoother melodic line. Example: A natural minor: A-B-C-D-E-F-G-A.
The Pentatonic Scale
A five-note scale formed by removing the half-step intervals from the major or minor scale, widely used in improvisation because it fits smoothly over almost any chord. Its structure is similar to traditional five-tone scales found in various folk music traditions around the world, making it feel intuitive in both Western and non-Western musical contexts. Example: C major pentatonic: C-D-E-G-A.
Church Modes
Seven scales formed by starting from each successive note of the major scale, each with its own distinct character: Ionian (identical to the major scale), Dorian, Phrygian, Lydian, Mixolydian, Aeolian (identical to the natural minor scale), and Locrian. Example: D Dorian: D-E-F-G-A-B-C-D (the same notes as C major, starting from D). Note: Modes are frequently used in jazz and film scoring to create a distinctive mood.
Triads
The most basic chord, built by stacking two notes a 3rd apart on top of a root note β there are four types: major, minor, augmented, and diminished triads. A major triad sounds bright, a minor triad sounds dark, an augmented triad has an unstable, rising quality, and a diminished triad sounds tense and unsettled. Which type you get depends on which kind of 3rd (major or minor) is stacked, and in what order. Example: C major triad: C-E-G / C minor triad: C-Eβ-G.
Seventh Chords
A richer, more jazz-flavored chord formed by adding one more note (a 7th) on top of a triad. Different combinations β major 7th, minor 7th, dominant 7th, half-diminished (minor 7 flat 5), and others β each produce a distinct color. Example: Cmaj7: C-E-G-B / C7 (dominant 7th): C-E-G-Bβ.
Diatonic Chords
The full set of chords built naturally by treating each note of a given key's scale as a root. Diatonic chords are labeled with Roman numerals (I, ii, iii, IV, V, vi, viiΒ°), where uppercase indicates a major chord, lowercase a minor chord, and Β° a diminished chord. Example: Diatonic chords in C major: C(I)-Dm(ii)-Em(iii)-F(IV)-G(V)-Am(vi)-Bdim(viiΒ°).
How to Read Chord Symbols
Understanding notation commonly seen on sheet music and lead sheets, like "Am7" or "G/B," makes chords much easier to read and use. A chord symbol is built from a letter (the root) plus a chord-quality label (m, maj7, 7, dim, etc.) plus any added tensions, in that order. A slash chord (like G/B) means the chord is G, but the lowest note (the bass note) should be B. Example: Am7 = A-C-E-G. G/B = bass note B, chord G (G-B-D).
Chord Function (Tonic, Subdominant, Dominant)
Diatonic chords can be grouped into three functional roles based on what they do within a piece: tonic (stable), subdominant (transitional), and dominant (tense). The tonic (I, vi) feels comfortable and stable, acting like the song's "home." The dominant (V, viiΒ°) creates strong tension that wants to resolve back to the tonic, while the subdominant (IV, ii) provides a natural bridge between the two.
Cadences
The way a chord progression brings a musical phrase or section to a close, functioning much like a period at the end of a sentence. An authentic cadence (VβI) provides the strongest, most complete sense of resolution. A plagal cadence (IVβI, sometimes called the "amen cadence") or a deceptive cadence (Vβvi, which breaks the expected resolution and moves elsewhere) create different flavors of closure.
Common Chord Progressions
Certain chord progression patterns repeat throughout popular music because they've proven to work well. The I-V-vi-IV progression is a classic pattern heard in countless pop songs, and vi-IV-I-V, along with I-vi-IV-V (a staple 1950s-style progression), are also widely used. Example: I-V-vi-IV in C major: C-G-Am-F.
The ii-V-I Progression (Jazz Harmony)
The most fundamental chord progression formula in jazz, moving through iiβVβI to create a smooth push and release of tension. Adding seventh chords or tensions to each chord can give it an even more distinctly jazz-flavored color. Example: ii-V-I in C major: Dm7-G7-Cmaj7.
Tension Chords (9th, 11th, 13th)
Extended chords that stack additional notes on top of a basic seventh chord for a richer, more colorful sound. Frequently used to create a sophisticated, dreamy quality in jazz, R&B, and city pop. Example: Cmaj9: C-E-G-B-D.
Modulation (Key Change)
A technique where a piece shifts to a different key partway through, creating a fresh mood and a sense of climax. This can be done smoothly using a shared "pivot" chord as a bridge, or more dramatically, by jumping abruptly up a half step or whole step.
Chord Substitution
Swapping in a different chord that shares the same function (tonic, subdominant, or dominant) to add fresh color to a familiar progression. In jazz, a common technique is tritone substitution, replacing a dominant V7 chord with another dominant chord a tritone (three whole steps) away.
Writing With Modes (Modal Composition)
An approach that steps outside the familiar framework of major and minor keys to write music that leans into the distinctive color of a specific church mode. Frequently used in film scoring, rock, and jazz to evoke a mysterious or exotic atmosphere.