Lydian_chord
In jazz music, the lydian chord is the major 7♯11 chord,[1] or ♯11 chord, the chord built on the first degree of the Lydian mode, the sharp eleventh being a compound augmented fourth. This chord, built on C, is shown below.
This is described as "beautiful" and "modern sounding."[1] The notes that make up the Lydian chord represent five of the seven notes of the Lydian mode, and the ♯11 at the top of the chord is the ♯4 (one octave higher) that distinguishes the Lydian mode from the major scale.
Major 7♯11 may also refer to the Lydian augmented chord, an augmented seventh chord with augmented fourth appearing in the Lydian augmented scale.[2]
In a chord chart the notation, "Lydian" indicates a major family chord with an added augmented eleventh, including maj7♯11, add9♯11, and 6♯11.[1]