Music Theory Basics

Music is built from a repeating cycle of 12 notes called the chromatic scale: C, C♯, D, D♯, E, F, F♯, G, G♯, A, A♯, B — then it repeats an octave higher. On a keyboard, the white keys are the "natural" notes (C, D, E, F, G, A, B) and the black keys are the sharps and flats in between.

Notice there's no black key between E–F or B–C — that's not a missing key, those two pairs are simply a half-step apart naturally.

The distance between any two adjacent keys — white or black — is a half step (also called a semitone). Two half steps make a whole step. Scales and chords are really just specific patterns of whole and half steps built from a starting note, or root.

A scale is a set of notes played in order, built from a repeating pattern of whole (W) and half (H) steps starting on a root note. The two you'll use constantly:

Major scale — pattern W–W–H–W–W–W–H. Starting on C, that pattern lands exactly on the white keys: C–D–E–F–G–A–B–C. This is why C major is the easiest key to see on a keyboard — no black keys involved.

Natural minor scale — pattern W–H–W–W–H–W–W. Starting on A, this also lands entirely on white keys: A–B–C–D–E–F–G–A. That's not a coincidence — A minor is the relative minor of C major: the same seven notes, just starting from a different point, which gives it a noticeably darker, sadder character even though nothing else changed.

Major generally sounds bright and resolved; minor sounds moody or introspective. Neither is "better" — genre and mood usually decide which one fits.

An interval is simply the gap between two notes, measured in half steps. Naming intervals sounds intimidating, but you only need a handful of them to understand chords and melody:

The 3rd and 5th matter most day to day — they're what turns a single note into a chord, covered next.

A triad is the simplest chord: three notes stacked in thirds — a root, a third, and a fifth. Which type of third and fifth you use decides the chord's quality:

• Major triad (root + major 3rd + perfect 5th) — bright, resolved. Example: C–E–G.
• Minor triad (root + minor 3rd + perfect 5th) — darker, moodier. Example: C–E♭–G.
• Diminished triad (root + minor 3rd + diminished 5th) — tense, unstable. Example: C–E♭–G♭.
• Augmented triad (root + major 3rd + augmented 5th) — unsettled, dreamlike. Example: C–E–G♯.

A C major triad: C–E–G.

Every major scale generates seven chords, one built on each note, and each gets a Roman numeral. In the key of C major:

Uppercase numerals are major chords, lowercase are minor. A huge number of songs across pop, rock, and folk lean on just four of these — the I, IV, V, and vi chords — in almost any order:

• I–V–vi–IV — an extremely common pop progression (C–G–Am–F in the key of C).
• I–IV–V — the backbone of blues and classic rock (C–F–G).
• vi–IV–I–V — the same four chords, a different starting point and mood (Am–F–C–G).

Try building a progression from these in GarageBand's chord strips or Musical Typing — it's a fast way to sketch something that already sounds musically "correct." Once these feel familiar, you'll start recognizing them in songs you already know — see How to Work Out Any Song's Chords by Ear.

A time signature (like 4/4) tells you two things: the top number is how many beats are in each measure (bar), and the bottom number is which note value counts as one beat.

• 4/4 ("common time") — 4 beats per measure, quarter note = 1 beat. The default for most pop, rock, and hip-hop.
• 3/4 — 3 beats per measure, quarter note = 1 beat. The classic "waltz" feel.
• 6/8 — 6 eighth notes per measure, usually felt as two groups of three rather than six separate beats.

Within a measure, note values divide time in half each step down:

This is exactly what GarageBand's quantize grid values (covered in the MIDI editing lesson) refer to — choosing "1/16" quantization snaps notes to the nearest sixteenth note.

Tempo, measured in BPM (beats per minute), sets how fast those beats go by. 60 BPM means one beat per second; 120 BPM means two beats per second. Faster tempos generally feel more energetic, slower tempos more relaxed — though genre convention matters more than any strict rule (a slow trap beat and a slow ballad can share a tempo and feel completely different).

For genre-specific tempo ranges and where to start, see Find Your Sound.