Music Theory I — How Music Works
You have been playing theory this whole time — now let us name it. The musical alphabet, how scales are built, what a key signature means, and the single most useful map in all of music: the circle of fifths. Click around it below and watch the key signatures change on the staff.
Concepts
The musical alphabet is A B C D E F G, then it repeats. A sharp (♯) raises a note one fret; a flat (♭) lowers it one fret.
On the guitar, one fret = a half step; two frets = a whole step.
The major scale is built with one fixed pattern of steps: W W H W W W H. Start it on any note and you have that note’s major scale.
A key signature lists the sharps or flats used for a whole piece. Each step clockwise on the circle of fifths adds one sharp; each step counter-clockwise adds one flat.
Every major key shares its notes with a relative minor — the inner ring of the circle. C major and A minor are the same seven notes.
Graduation
Without looking: how many sharps does A major have, and what is its relative minor? Then check yourself on the circle.