Music Theory

This deck is a friendly starting point for learning the language of music, with a focus on the building blocks you'll encounter most often as a musician. The cards walk through different types of scales, including major, natural minor, harmonic minor, melodic minor, pentatonic, blues, whole tone, and chromatic scales. Alongside scales, you'll find questions about intervals, including what they are, how to recognize perfect intervals, and how to tell major and minor intervals apart.

It's well suited for beginners just dipping their toes into theory, as well as intermediate players who want to firm up the fundamentals behind what they already play by ear. If you sing, play an instrument, or write music, the material here will help you understand why certain notes sound the way they do and how to use them more intentionally.

To get the most out of your study sessions, try working through the cards a few at a time rather than cramming everything in one sitting. Scales and intervals are easiest to absorb when you can hear them, so humming, singing, or playing the notes on an instrument as you review will help the patterns stick in your memory far better than reading alone. Spacing your reviews over several days will also give your brain time to lock in each concept before moving on to the next.

A scale is a sequence of notes arranged in ascending or descending order that forms the melodic and harmonic foundation of a piece. The most fundamental scale in Western music is the major scale, which follows the interval pattern whole-whole-half-whole-whole-whole-half. The C major scale, consisting of C, D, E, F, G, A, B, contains no sharps or flats and is the simplest major scale to play on the piano because it uses only the white keys. Every major scale follows the same intervallic structure, just starting on different pitches and incorporating different accidentals.

Minor scales come in three principal forms, each with a distinct character. The natural minor scale follows the pattern whole-half-whole-whole-half-whole-whole, which produces a darker, more melancholic sound compared to the major scale because it lowers the third, sixth, and seventh scale degrees. The harmonic minor scale raises the seventh degree of the natural minor by a half step; this creates an augmented second interval between the sixth and seventh degrees and provides a leading tone that pulls strongly toward the tonic. The melodic minor scale further raises the sixth degree along with the seventh when ascending, eliminating the augmented second; in classical practice, it reverts to the natural minor when descending.

Beyond seven-note scales, the pentatonic scale uses only five notes per octave. The major pentatonic consists of scale degrees 1, 2, 3, 5, and 6 of the major scale, following the interval pattern whole-whole-minor third-whole-minor third. The minor pentatonic uses 1, ♭3, 4, 5, and ♭7, and is one of the most widely used scales in rock, blues, and pop guitar. The A minor pentatonic, for example, contains A, C, D, E, G. The blues scale is a minor pentatonic with an added ♭5 blue note, creating a chromatic passing tone that gives blues music its characteristic sound. Other specialized scales include the whole tone scale, consisting of six notes each a whole step apart with a dreamy and ambiguous quality, and the chromatic scale, which includes all twelve pitches within an octave, each a half step apart.

The seven diatonic modes offer additional tonal colors by starting the major scale on each of its seven scale degrees. The Ionian mode, beginning on the first degree, is identical to the major scale, while the Aeolian mode, beginning on the sixth degree, is identical to the natural minor scale. Between them lie the Dorian mode, with a raised sixth giving it a slightly brighter, jazzy quality; the Phrygian mode, with a distinctive half step between the first and second degrees evoking Spanish or Middle Eastern flavors; the Lydian mode, with a raised fourth degree producing a dreamy, floating character; the Mixolydian mode, which is a major scale with a lowered seventh forming the basis of dominant seventh chords; and the Locrian mode, whose diminished fifth above the tonic makes it the most unstable mode and rarely used as a tonal center.

An interval is the distance in pitch between two notes, described by a numeric value that indicates how many letter names are spanned, and a quality that specifies the exact number of half steps. The perfect intervals are the unison, perfect fourth, perfect fifth, and perfect octave. These are called perfect because of their strong consonance and because they have no major or minor variants; they are classified only as perfect, augmented, or diminished.

Major and minor intervals differ by a single half step. A minor interval is one half step smaller than its corresponding major interval; for instance, a major third spans four half steps (as in C to E), while a minor third spans three half steps (as in C to E♭). Augmented intervals are one half step larger than a perfect or major interval, so a perfect fifth of seven half steps becomes an augmented fifth of eight half steps. Diminished intervals are one half step smaller than a perfect or minor interval; reducing a perfect fifth yields a diminished fifth of six half steps, which is also known as a tritone.

The tritone, an interval of three whole steps or six half steps, holds particular significance in tonal music. It divides the octave exactly in half and produces maximum dissonance. Tritones appear prominently in dominant seventh chords, where they create the harmonic tension that resolves to the tonic. Tritones have two common spellings: an augmented fourth and a diminished fifth. These two spellings are enharmonic intervals, meaning they sound identical but are notated and analyzed differently because they belong to different keys. For example, an augmented fourth from C to F♯ and a diminished fifth from C to G♭ both span six half steps but carry distinct theoretical functions.

Intervals can also be inverted by moving the lower note up an octave or the upper note down. The numeric sizes add up to nine, so a third inverts to a sixth and a fourth inverts to a fifth, while the qualities invert as well: major becomes minor, augmented becomes diminished, and perfect intervals remain perfect. When an interval exceeds an octave, it is called a compound interval: a ninth is a compound second, a tenth is a compound third, and so on, sharing the same quality as its simple counterpart. A major sixth, for instance, spans nine half steps and is the inversion of a minor third.

A triad is a three-note chord built by stacking two thirds on top of a root note. The four basic triad qualities are major, minor, augmented, and diminished. A major triad contains a root, a major third, and a perfect fifth, with four half steps between the root and third and three between the third and fifth. A minor triad uses a root, minor third, and perfect fifth, reversing the half-step distribution. An augmented triad consists of a root, major third, and augmented fifth and is built from two stacked major thirds, giving it a tense, unresolved quality. A diminished triad consists of a root, minor third, and diminished fifth and is built from two stacked minor thirds, sounding unstable and typically resolving to a more consonant chord.

Seventh chords extend triads by adding another third on top, producing four-note harmonies. The dominant seventh chord is a major triad with an added minor seventh, and contains a tritone between its third and ♭7th that drives resolution to the tonic. The major seventh chord is a major triad with an added major seventh, producing the smooth, lush sound characteristic of jazz, bossa nova, and R&B. The minor seventh chord is a minor triad with an added minor seventh and is the most common seventh chord built on the ii, iii, and vi degrees of a major key. The diminished seventh chord stacks a diminished seventh on a diminished triad and, because it consists entirely of stacked minor thirds, is perfectly symmetrical. The half-diminished seventh chord is a diminished triad with an added minor seventh, and frequently functions as the ii chord in minor keys.

Beyond seventh chords, extended chords add further chord tones above the octave. A ninth chord is a seventh chord with an added ninth, which is a second above the octave. Eleventh and thirteenth chords continue stacking thirds, adding the eleventh (a fourth above the octave) and the thirteenth (a sixth above the octave). In practice, musicians often omit certain tones, particularly the fifth and sometimes the eleventh, to avoid muddy voicings. Two other common chord alterations are the suspended chord, which replaces the third with the second (sus2) or fourth (sus4), creating an open sound that lacks major or minor quality, and the power chord, which contains only the root and perfect fifth, making it neither major nor minor and a staple of rock and metal music.

The order of notes in a chord can be rearranged through chord inversion, in which a note other than the root is placed in the bass. A triad in first inversion has the third in the bass, second inversion has the fifth in the bass, and so on. Inversions are often written using slash-chord notation, such as C/E for a C major chord with E in the bass. Inversions allow smoother voice leading and create different bass-line possibilities. The diatonic triads in any major key follow a predictable quality pattern: I (major), ii (minor), iii (minor), IV (major), V (major), vi (minor), and vii° (diminished), forming the foundation of Western harmonic function.

A few foundational chord progressions recur throughout Western music. The I–IV–V–I progression cycles through tonic, subdominant, dominant, and back to tonic and is the bedrock of countless songs across genres. In C major, this is C–F–G–C. The ii–V–I progression is the most important progression in jazz harmony; the ii chord provides smooth voice leading into the dominant V7, which then resolves to the tonic. In C major, this is Dm7–G7–Cmaj7.

The 12-bar blues form follows a three-line chord pattern, typically I–I–I–I / IV–IV–I–I / V–IV–I–I (with the last bar sometimes using V as a turnaround), and is the foundation of blues, rock and roll, and early jazz. In the key of A, this uses A7, D7, and E7. The I–V–vi–IV progression is one of the most common pop progressions; sometimes called the four-chord song or the Axis of Awesome progression, it has appeared in hundreds of hit songs. In C major, this is C–G–Am–F. To make transposition easier, the Nashville Number System represents chords as scale-degree numbers rather than letter names, so the same numeral pattern describes the progression in any key.

Beyond these core progressions, several harmonic devices add variety and motion. A deceptive cadence occurs when the dominant V chord resolves not to the expected tonic but to another chord, most commonly vi, creating surprise while still providing a sense of harmonic arrival. A secondary dominant is a dominant seventh chord that tonicizes a chord other than the tonic; in C major, for example, D7 functions as V7/V because it is the dominant of G. Secondary dominants introduce chromatic color and forward momentum without leaving the home key, and they are commonly used to add interest within otherwise diatonic progressions.

Rhythm is organized through meter, which groups beats into recurring patterns called measures. A time signature, placed at the beginning of a piece, indicates both how many beats are in each measure and which note value receives one beat. The 4/4 time signature, also called common time and often denoted by a C symbol, has four quarter-note beats per measure and is the most widely used meter in Western music.

Meters fall into two broad categories. In simple time, each beat divides naturally into two equal parts, as in 4/4 or 3/4. In compound time, each beat divides into three equal parts, and the top number is typically a multiple of three. A 6/8 meter has six eighth notes per measure grouped into two beats of three eighth notes each, producing the lilting feel of jigs, marches, and slow ballads. A 3/4 meter, commonly known as waltz time, has three quarter-note beats per measure with a strong-weak-weak pattern and is the signature meter of waltzes and minuets. Asymmetric or irregular meters such as 5/4, often grouped 3+2 or 2+3, create an uneven, driving feel heard in pieces like Dave Brubeck's Take Five and the Mission: Impossible theme.

Notes and rests are the building blocks of rhythm. From longest to shortest in 4/4 time, note values are whole (4 beats), half (2 beats), quarter (1 beat), eighth (½ beat), sixteenth (¼ beat), and thirty-second (⅛ beat), each half the duration of the previous one. A dotted note increases a note's duration by half its original value, so a dotted half note equals three beats and a dotted quarter note equals 1.5 beats. Rests mirror note values: a whole rest hanging from a line equals four beats, a half rest sitting on a line equals two beats, and quarter, eighth, and sixteenth rests equal one beat, half a beat, and a quarter beat respectively.

Several rhythmic techniques add complexity and interest. Syncopation emphasizes weak beats or offbeats, disrupting the expected pattern of accents and creating rhythmic tension and forward momentum; it is a defining feature of jazz, funk, reggae, and Latin music. A tuplet divides a beat into a number of equal parts different from the standard division; the most common is the triplet, which divides a beat into three equal parts in simple time, though quintuplets and septuplets also occur. A tie connects two notes of the same pitch, combining their durations into one sustained note, while a slur connects notes of different pitches to indicate they should be played smoothly. A hemiola is a rhythmic device in which two groups of three beats are reinterpreted as three groups of two beats, or vice versa, and is a common feature of Baroque and Latin music.

A key signature is a set of sharps or flats placed at the beginning of a staff, after the clef, that indicates which notes are consistently raised or lowered throughout a piece. The key signature establishes the key and eliminates the need for repeated accidentals. Sharps and flats appear in key signatures in a specific order dictated by the circle of fifths. Sharps are added in the order F♯, C♯, G♯, D♯, A♯, E♯, B♯, easily remembered with the mnemonic Father Charles Goes Down And Ends Battle, where each new sharp is added a perfect fifth above the previous one. Flats appear in the reverse order: B♭, E♭, A♭, D♭, G♭, C♭, F♭, summarized as Battle Ends And Down Goes Charles' Father, with each new flat a perfect fourth above the previous one.

Identifying the major key from a key signature follows simple rules. For sharp key signatures, the major key is one half step above the last sharp: if the last sharp is F♯, the key is G major; if it is C♯, the key is D major. For flat key signatures with two or more flats, the major key is the second-to-last flat, so two flats (B♭ and E♭) indicate B♭ major. The exception is a single flat, which indicates F major. G major has one sharp, F♯; D major has two sharps, F♯ and C♯; and E♭ major has three flats, B♭, E♭, and A♭, and is a popular key for brass instruments and wind ensemble music.

Some keys are enharmonic, meaning they sound identical but are spelled differently. F♯ major (six sharps) and G♭ major (six flats) contain exactly the same pitches, as do B major and C♭ major, and D♭ major and C♯ major. The circle of fifths arranges all twelve keys in a circle with each key a perfect fifth apart from its neighbors: moving clockwise from C adds one sharp per step, while moving counterclockwise adds one flat per step. The circle is an essential tool for understanding key relationships, modulation, and the order of accidentals.

Every major key has a relative minor that shares the same key signature. The relative minor is found by going down a minor third from the major tonic, which lands on the sixth scale degree of the major scale; for example, the relative minor of C major is A minor, and both keys share the key signature of no sharps or flats. Modulation is the process of changing from one key to another within a piece, while transposition is the process of shifting all notes in a piece up or down by a constant interval while preserving melodic and harmonic relationships. Transposition is often used to accommodate a singer's range or to write parts for transposing instruments, instruments whose written pitch differs from their sounding pitch, such as the B♭ clarinet, B♭ trumpet, F horn, E♭ alto saxophone, and B♭ tenor saxophone.

Musical notation provides the visual framework for communicating pitch and rhythm. The treble clef, also called the G clef, curls around the second line of the staff to indicate that line is G4, and is used for higher-pitched instruments and voices as well as the right hand in piano music. The bass clef, also called the F clef, places two dots around the fourth line to mark it as F3, and is used for lower-pitched instruments, voices, and the left hand in piano music. Several symbols modify pitch within a measure: the sharp (♯) raises a note by a half step, the flat (♭) lowers it by a half step, the natural (♮) cancels a previous accidental or key signature alteration, and the double sharp and double flat alter a note by a whole step.

Other symbols affect duration and articulation. A fermata placed over a note or rest instructs the performer to hold it longer than its written value, at the performer's or conductor's discretion. Staccato, marked by a dot above or below a note, directs the performer to play the note short and detached, typically held for about half its written value. Legato indicates that notes should be played smoothly and connected, often marked by a slur, a curved line over notes of different pitches. A tie, by contrast, connects two notes of the same pitch to combine their durations into one sustained note. Repeat signs are double barlines with two dots that indicate a section should be played again, with first and second endings directing different passages on each repetition. D.C. (Da Capo) instructs the performer to return to the beginning of the piece, and D.S. (Dal Segno) instructs a return to the segno sign; both are often followed by al Fine or al Coda to guide the performer through the structure.

Dynamics and tempo shape the emotional contour of a piece. The dynamic marking piano (p) means softly and forte (f) means loudly; doubling either, as in pianissimo (pp) or fortissimo (ff), makes them more extreme. Mezzo piano (mp) means moderately soft and mezzo forte (mf) means moderately loud. A crescendo gradually increases volume, marked by an opening hairpin, while a decrescendo, also called a diminuendo, gradually decreases volume, marked by a closing hairpin. Common tempo markings include Largo (very slow, around 40–60 BPM), Adagio (slow and expressive, around 66–76 BPM), Andante (a moderately slow walking pace, around 76–108 BPM), Allegro (fast and lively, around 120–156 BPM), and Presto (very fast, around 168–200 BPM).

Form organizes music into larger structures. Binary form consists of two contrasting sections, often used in Baroque dances like gavottes and bourées. Ternary form features a returning first section after a contrasting middle, providing symmetry and closure, and is common in da capo arias, minuets with trios, and many pop songs. Rondo form alternates a recurring main theme with contrasting episodes, such as A–B–A–C–A, and was a popular final-movement form in Classical sonatas and concertos. Sonata form structures entire movements in three main sections: an exposition introducing two contrasting themes in different keys, a development that transforms and explores those themes, and a recapitulation that restates both themes in the home key. Theme and variations presents a melody and then repeats it with successive modifications to melody, harmony, rhythm, tempo, key, or orchestration. The 12-bar blues form consists of three four-bar phrases following the chord pattern I–I–I–I / IV–IV–I–I / V–IV–I–I and typically uses an AAB lyrical structure in which the first line is stated and then repeated before a contrasting third line.