A piano is now docked at the bottom of your screen. Every time you press a ▶ Play button anywhere in this guide, the exact keys you'd need to press light up — gold for the root note, crimson for the rest. Scales light up step by step, and chord progressions show each chord as it sounds. It even works with the sound muted, and you can click its keys directly to explore.
Try it now:
Music theory is the language musicians use to describe why certain notes, chords, and rhythms sound the way they do. It won't tell you what to play — it explains what you're already hearing.
Think of it like learning grammar after you already speak a language. You don't need theory to make music, but it helps you understand, communicate, and grow much faster.
Western music uses 12 notes, each a semitone (half-step) apart. After 12 steps, you're back to the same note — just one octave higher. These 12 notes repeat forever up and down your instrument.
The smallest step — moving to the very next key on a piano (white or black). C → C# is a semitone. E → F is also a semitone (no black key between them).
Two semitones combined. C → D is a whole tone (you skip C#). A whole tone = 2 half-steps.
A scale is a specific selection of notes from the 12, arranged in a pattern of steps. The pattern of whole steps (W) and half steps (H) determines the scale's character — and crucially, it's the same pattern in every key. That's why you can play a major scale starting on any note.
The Major scale uses the pattern W – W – H – W – W – W – H. Starting on C, that gives you the 7 white keys: C D E F G A B. Below, the gaps between notes show whether each step is a Whole step (2 keys) or Half step (1 key):
A key is the home base of a piece of music. When a song is "in the key of C major," it mostly uses the notes from the C Major scale, and the note C feels like "home" — stable and resolved.
You can think of the key as the tonal center that everything else orbits around.
A chord is 3 or more notes played at the same time. The most common chords are triads — built by stacking every other note of a scale.
Root + Major 3rd + Perfect 5th. Sounds bright and happy.
Root + Minor 3rd + Perfect 5th. Sounds darker and sadder.
Musicians number chords by their position in the scale using Roman numerals. This lets you describe a progression that works in any key.
| Scale Degree | Roman | Quality | In C |
|---|---|---|---|
| 1st | I | Major | C |
| 2nd | ii | minor | Dm |
| 3rd | iii | minor | Em |
| 4th | IV | Major | F |
| 5th | V | Major | G |
| 6th | vi | minor | Am |
| 7th | vii° | dim° | B° |
Here's a suggested order for beginners. You don't have to follow it strictly — jump around as your curiosity leads you.
Moving to a higher-pitched note. On piano: moving right. On guitar: moving toward higher-numbered frets, or thinner strings.
Moving to a lower-pitched note. On piano: moving left. On guitar: moving toward lower-numbered frets, or thicker strings.
Between most letter names, there's a half-step gap that is filled by a sharp or flat. The exceptions are E–F and B–C — these are already only a half-step apart, so there's no note in between.
Only a half-step apart. No black key between E and F on the piano. This is why the major scale pattern has a half-step between degrees 3 and 4.
Only a half-step apart. No black key between B and C on the piano. This is why the major scale has a half-step between degrees 7 and 8 (the octave).
Five lines and four spaces. Each line and space is the next letter of the musical alphabet (A–G), so moving up one step on the staff moves up one letter. Sharps and flats aren't separate positions — they're marked with ♯ and ♭ signs in front of the note.
Its curl wraps the G line (G above middle C). Lines bottom-to-top: E G B D F — Every Good Boy Does Fine. Spaces spell F A C E. Used for melodies, vocals, leads and the piano's right hand.
Its two dots sit either side of the F line (F below middle C). Lines: G B D F A — Good Boys Do Fine Always. Spaces: A C E G — All Cows Eat Grass. Used for bass, 808 lines and the left hand.
Notes that run off the staff get short extra lines called ledger lines. Middle C (C4) sits on one ledger line just below the treble staff — and just above the bass staff. Same note, both clefs: it's where the two staves meet on a piano score.
♯ sharp raises a note a semitone, ♭ flat lowers it, ♮ natural cancels either. Instead of writing the same sharps on every note, music starts with a key signature — the sharps or flats that apply to the whole piece. See Key Signatures.
The note's shape tells you how long it lasts — whole, half, quarter, eighth, sixteenth — and rests are silences of the same lengths. All of that is in Time Signatures & Note Values.
| Interval | Semitones | Abbr | Example (from C) | Sound / Quality | Ear Training |
|---|
| Degree | Name | In C | What it does |
|---|---|---|---|
| 1 | Tonic | C | Home. Total rest — everything resolves here. |
| 2 | Supertonic | D | Mild tension, one step above home. |
| 3 | Mediant | E | Midway to the 5th — it’s what makes the key major or minor. |
| 4 | Subdominant | F | Pulls away from home; sets up the dominant. |
| 5 | Dominant | G | The strongest pull back to the tonic. |
| 6 | Submediant | A | The root of the relative minor. |
| 7 | Leading Tone | B | A half-step below home — it “leads” your ear up to the tonic. |