Music theory The basics
Scales and keys
Major, minor and pentatonic scales, key signatures, the order of sharps and flats, relative keys and the circle of fifths.
Practise this on its own page: Scale player, Circle of fifths.
What a scale is
A scale is a set of notes in step order, starting and ending on the same letter name. The first note is the tonic, which acts as the home note of the key.
Each step of the scale also has a name: tonic, supertonic, mediant, subdominant, dominant, submediant and leading note (leading tone), then the tonic again an octave higher.
The major scale
Every major scale follows the same pattern of tones (T) and semitones (S) going up: T T S T T T S. C major uses only the white keys of the piano: C D E F G A B C.
If you start the same pattern on another note, you will need sharps or flats to keep the pattern correct.
Natural minor
The natural minor scale uses the pattern T S T T S T T, going up and coming down. A natural minor uses only white keys: A B C D E F G A.
Harmonic and melodic minor
The harmonic minor raises the 7th note by a semitone, so it leads strongly back to the tonic. In A harmonic minor the G becomes G#.
The melodic minor raises both the 6th and 7th notes on the way up, then uses the natural minor on the way down. In A melodic minor you play F# and G# going up, then G and F coming down.
Pentatonic and chromatic scales
A pentatonic scale has five notes. The major pentatonic uses notes 1, 2, 3, 5 and 6 of the major scale, so C major pentatonic is C D E G A.
The minor pentatonic uses the same notes as a major pentatonic but starts on its 5th note (the 6th degree of the major scale). A minor pentatonic is A C D E G.
A chromatic scale uses all twelve semitones in a row.
Key signatures and the order of sharps and flats
A key signature is a group of sharps or flats written after the clef and before the time signature. It saves writing the same accidentals over and over again.
Sharps are always added in the order F C G D A E B. Flats are added in the reverse order: B E A D G C F.
Quick tricks for major keys: with sharps, the key is one semitone above the last sharp. With flats, the key is the second-to-last flat. F major, with one flat (B-flat), is worth learning by heart.
Relative keys and the circle of fifths
A major key and a minor key that share the same key signature are called relative keys. The minor key's tonic is always three semitones below its relative major's tonic, so A minor is the relative minor of C major.
Parallel keys share the same tonic but have different key signatures, such as C major and C minor.
The circle of fifths arranges the keys in a circle, each a 5th away from the next. Going clockwise from C major adds one sharp at a time, and going anticlockwise adds one flat at a time. Many charts show the relative minor keys on the inside of the circle.