Music theory
Music theory gives names to what you hear: where a note sits on the staff, how long it lasts, and how notes stack into scales and chords.
- 1Reading notesLearn to read pitches on the staff: treble clef, bass clef, ledger lines, the grand staff, sharps and flats, and the different names musicians use for the same notes. Every unit has a staff quiz or a keyboard you can play.8 Units
- 2Rhythm and meterHow music is measured in time: the beat and tempo, note values and rests, dots and ties, simple meters like 3/4 and 4/4, compound meters like 6/8, and syncopation, triplets and pickups. Every unit has the rhythm lab with a tap-along test that scores each tap in milliseconds, and most units add a metronome for any time signature and note blocks you stack into bars.6 Units
- 3Scales and keysBuild any major scale from one pattern of whole and half steps, name every scale degree, read a key signature at a glance, find your way around the circle of fifths, and tell a minor key from its relative major.6 Units
- 4IntervalsAn interval is the distance between two notes. Count half steps on the keyboard, name thirds, fourths, fifths and octaves, hear why some intervals sound stable, and train your ear and voice with melodies everyone knows.8 Units
- 5ChordsStack thirds to build triads, hear the difference between major, minor, diminished and augmented, name every chord in a key with Roman numerals, read inversions and seventh chords, and follow the progressions and cadences that end a musical phrase.6 Units
Five courses, read in this order
The subject has five courses and 34 units. Start with Reading notes, so you can read every later example, and Rhythm and meter, which covers the time side of the page. Intervals measures the distance between two notes and underlies the last two courses. Scales and keys builds scales out of intervals, and Chords builds harmony out of scales. Most units add a staff quiz, a playable keyboard or an ear test, so you check each rule by sound as well.
Pitch on the staff, time in the bar
A staff has five lines and four spaces, counted from the bottom. In the treble clef the lines are E G B D F and the spaces spell F A C E. The bass clef is the F clef, and its two dots frame F3. Middle C, or C4, sits on one ledger line between the two staves of the grand staff. A sharp raises a note by a half step and a flat lowers it, so one black key can carry two names, C sharp and D flat. A later unit compares the names other systems use: do re mi in fixed and movable do, and German, where H means B.
The rhythm course starts from the beat. One beat lasts 60 divided by the BPM in seconds, so at 120 BPM a beat is half a second. Each note value lasts half the one before it, and a dot adds half again. Simple meters like 3/4 divide the beat into two, compound meters like 6/8 divide it into three, and 3/4 and 6/8 fill the same length with different groupings. Every unit has a rhythm lab where a tap-along test scores each tap in milliseconds.
Distance between two notes
A half step is the next key on the keyboard, black or white, and there are 12 in an octave. A major third spans 4 half steps, a minor third 3, a perfect fourth 5 and a perfect fifth 7. An octave doubles the frequency, which is why letter names repeat. The course links each interval to a tune you already know, such as the rising fifth at the start of Twinkle, Twinkle, Little Star, and then trains the ear without them, a few minutes a day.
Key signatures, triads and cadences
Every major scale follows one pattern of steps: whole, whole, half, whole, whole, whole, half. Sharps enter a key signature in the order F C G D A E B, and the circle of fifths adds one more with each fifth you climb. A relative minor shares its major key signature, with its tonic 3 half steps lower. Chords stack thirds: a major triad is 4 plus 3 half steps, minor 3 plus 4, diminished 3 plus 3, augmented 4 plus 4. Roman numerals name each chord in a key, I ii iii IV V vi vii°, so a progression can move to any key. The last unit ends on cadences: authentic V to I, plagal IV to I, a half cadence on V, and deceptive V to vi.
Questions about this subject
How do I build a triad?
Choose a starting note and stack two thirds above it, giving a root, third and fifth. Beginning with C produces the letter names C, E and G because each step skips one letter. Accidentals then determine the chord quality, so building a triad on D requires considering F sharp if you want D major rather than assuming every white-key stack is major. Chords
What changes a major triad into a minor triad?
Lowering the third by a half step changes C, E, G into C, E flat, G. A major triad stacks a four-half-step third below a three-half-step third, while a minor triad reverses those sizes. Both retain the perfect fifth spanning seven half steps from root to fifth, so the change is in the middle note rather than the outer interval. Chords
Is the lowest note always the root of a chord?
Only in root position: the bass is the lowest sounding note, while the root identifies the note on which the chord is built. E, G, C still belongs to a C chord even though E is lowest. That arrangement is first inversion, while placing G lowest makes second inversion without changing the root from C. Chords
What does a slash chord such as C/E mean?
The letter before the slash names the chord and the note after it specifies the bass. C/E therefore asks for a C chord with E as the lowest note, not a new chord whose root has become E. Slash notation can create a smoother bass line, as C, G/B and Am let the bass descend C, B, A. Chords
Does doubling a note or spreading the notes change a chord’s name?
Not by itself: repeating C or E and placing notes in different octaves can still leave the same C-major triad. A guitarist and pianist can therefore voice the chord differently while using the same pitch-name set. To identify a widely spaced chord, collect its notes into a compact stack of thirds and find the root of that stack. Chords