In jazz and blues, blue notes are notes sung or played at a lower pitch than those of the major scale for expressive purposes. Typically the alteration is less than a semitone, but this varies among performers.
The blue notes correspond approximately to the flatted third, flatted fifth, and flatted seventh scale degrees, although they approximate non-equal tempered pitches found in African work songs; specifically, the flatted seventh may often be a justly tuned minor seventh. Blue notes are the most important notes in the blues scale.
Now I'm confused. Are you saying that playing blue notes are basically a penatonic scale with a diminished fifth, or that blue note is a term for a flatted fifth or augmented fourth?
