Blues, tension and improvisation

Minor blues notes over a major chord

The C minor blues scale is C–E♭–F–G♭–G–B♭: 1–♭3–4–♭5–5–♭7. Over C7, C–E–G–B♭, melodic E♭ meets the chord's E. This mixture of minor and major thirds is an important part of blues. It can sound tense, and its effect depends on phrasing, register and style.

The piano uses fixed pitches as an approximation. Singers and many instrumentalists can shape blue notes between those fixed pitches. The blues scale is a practical selection of keys, not a complete description of blues sound.

Twelve bars give you a map

A basic 12-bar blues in C can be C7 | C7 | C7 | C7 | F7 | F7 | C7 | C7 | G7 | F7 | C7 | G7. Many variations exist. The numerals I7, IV7 and V7 describe a blues pattern; all three chords have dominant-seventh quality. They do not all come from a single C major scale.

Here “dominant seventh” names the chord quality: a major triad plus a minor seventh. It does not mean that all three chords have dominant function. C7 can be the home chord in C blues. F7 contains E♭ and C7 contains B♭, so the progression goes beyond the C major collection.

Let the chord change affect the phrase

A C blues scale can work throughout the progression in many blues styles, but its notes take on different meanings over C7, F7 and G7. Try landing on A when F7 arrives: it is the chord's third even though A is outside the C minor blues scale. Following the harmony expands your vocabulary.

Make music with a few notes

Play a short idea, give it a pause and answer with a variation. Repeat the rhythm, change one note or alter the ending as the chord changes. A small vocabulary helps you hear the relationships. The goal is a phrase with shape, direction and space rather than the largest possible number of notes.

Try it at the piano

Start the twelve bars below and count four beats per bar. On your own piano, begin with just C, E♭ and G. Listen for F7 in bar five and try landing on A. Playback gives you one complete round and stops after bar 12.