In jazz and blues, a blue note (also "worried" note) is a note that—for expressive purposes—is sung or played at a slightly different pitch than standard. Typically the alteration is between a quartertone and a semitone, but this varies among performers and genres.

Blue Note Records is an American jazz record label, established in 1939 by Alfred Lion and Max Margulis. Francis Wolff became involved shortly afterwards. It derives its name from the characteristic "blue notes" of jazz and the blues.