An interval is the distance between two notes. Intervals are the building blocks for chords, melodies, and harmonies.
Intervals can be unison, second, third, fourth, fifth, sixth, seventh, or octave. They can also be qualified as major, minor, perfect, augmented, or diminished.
Bass Tip: Bass lines often use perfect fifths and octaves to outline chords. Practicing interval shapes helps you navigate common bass figures.
Generic intervals (or “basic intervals”) are counted by letter names only. For example, from C to E is always called a “third” (C–D–E = 1–2–3) regardless of sharps or flats.
Another example: C to E or C to Eb are both generically “thirds”; the exact quality (major or minor) is determined by the number of semitones.
Specific intervals account for the exact semitone distance. For seconds, thirds, sixths, and sevenths, intervals can be major, minor, augmented, or diminished. For unisons, fourths, fifths, and octaves, intervals are perfect, augmented, or diminished.
To write or spell an interval correctly:
Example: Generic interval from C to G is a fifth. To make it a perfect fifth, you need 7 semitones between C and G.
Inverting an interval means flipping its notes so the lower note becomes higher or vice versa. The sum of a diatonic interval and its inversion is always 9 (e.g., a 3rd inverts to a 6th, 4th inverts to a 5th).
Bass Tip: Inversion knowledge helps analyze chords in various voicings, especially for smooth bass lines.