Upper structure
In jazz, the term upper structure or "upper structure triad" refers to a voicing approach developed by jazz pianists and arrangers defined by the sounding of a major or minor triad in the uppermost pitches of a more complex harmony.These form a tritone which defines the dominant sound, and are the major 3rd and minor 7th of the C7♯9 chord.(Note: the root C is omitted here, and is often done so by jazz pianists for ease of playing, or because a bass player is present.)[2] For instance, in example one above (C7♯9) the triad of E♭ major is a (compound) minor 3rd away from C (root of the bottom chord).Other possible upper structures are: The second item in the list above (C7♭9♯11) has a related version called upper structure sharp four minor--with the written shorthand US♯iv--created with an F♯ minor triad.