The Music Stem / The Musician's Library / Composer's Handbook / Upper-Structure Triad
Composer's Handbook
An upper-structure triad places a simple triad above a seventh chord to add color tones.
Place a D major triad above C7.
C–E–B♭ with D–F♯–A above: D is the 9th, F♯ the ♯11th, A the 13th (C13♯11).