Blue Note
A slightly lowered third, fifth, or seventh, characteristic of blues and jazz.
What it means
A blue note is a note, usually the third, fifth, or seventh degree of a major scale, that is intoned slightly lower than in equal temperament, or left indeterminate between two semitones. This peculiar "hovering" pitch produces the plaintive, expressive sound associated with blues and jazz.
On fixed-pitch Western keyboard instruments, blue notes can only be approximated, so they are often suggested there through ornaments such as small grace notes or glissandos.
Musical use
Blue notes trace back to African American musical traditions, in which pitch was treated more freely and flexibly than European major-minor tonality allows. They are a central expressive device of the blues and were carried from there into jazz, rhythm and blues, and numerous styles of popular music.
The blue note should be distinguished from a regular chromatic alteration in the sense of classical harmony, since it is not fixed to one exact pitch but relies precisely on its blurriness between the semitones.
Performance practice
When playing blue notes on a fixed-pitch instrument, you can recreate the characteristic effect through a slight bend of the note, a brief ornament, or deliberately imprecise intonation. On the voice or on instruments with continuously variable pitch, such as guitar or violin, the blue note can be shaped directly and flexibly.