Music theory is the language musicians use to describe how music works. This guide covers the three fundamental building blocks — scales, intervals and chords — that every musician should understand.
A scale is a sequence of notes ordered by pitch. The major scale follows the pattern: whole-step, whole-step, half-step, whole-step, whole-step, whole-step, half-step (W-W-H-W-W-W-H). Starting on C, this gives all white keys: C-D-E-F-G-A-B-C. The natural minor scale follows W-H-W-W-H-W-W. Harmonic minor raises the 7th note; melodic minor raises the 6th and 7th ascending.
An interval is the distance between two pitches, measured in half-steps. From smallest to largest: minor 2nd (1 half-step, Jaws theme), major 2nd (2, Happy Birthday), minor 3rd (3, Greensleeves), major 3rd (4, When the Saints), perfect 4th (5, Here Comes the Bride), tritone (6, The Simpsons), perfect 5th (7, Twinkle Twinkle), minor 6th (8, Love Story theme), major 6th (9, My Bonnie), minor 7th (10, Star Trek theme), major 7th (11, Take On Me), octave (12, Somewhere Over the Rainbow).
A triad is a three-note chord built by stacking thirds. Major triad: root + major 3rd + perfect 5th. Minor triad: root + minor 3rd + perfect 5th. Diminished: root + minor 3rd + diminished 5th. Augmented: root + major 3rd + augmented 5th. Seventh chords add a fourth note: major 7th, minor 7th, dominant 7th (major triad + minor 7th), half-diminished and fully-diminished.
Roman numerals label chords by scale degree: I (tonic), ii (supertonic, minor), iii (mediant), IV (subdominant, major), V (dominant, major), vi (submediant, minor), vii° (leading tone, diminished). The most common progression in popular music is I-V-vi-IV. In C major: C-G-Am-F. The ii-V-I progression is the backbone of jazz harmony.
Download our free music theory worksheets for note naming, interval identification and chord building practice. Print our blank chord charts to map out progressions, and keep a Circle of Fifths poster handy for key reference.