The diminished seventh chord is a four-note chord (a seventh chord) composed of a root note, together with a minor third, a diminished fifth, and a diminished seventh above the root: (1, 3, 5, 7). For example, the diminished seventh chord built on C, commonly written as C7, has pitches C–E–G–B (A): As such, a diminished seventh chord comprises a diminished triad plus a diminished seventh. Because of this, it can also be viewed as four notes all stacked in intervals of a minor third and can be represented by the integer notation {0, 3, 6, 9}. Since a diminished seventh interval is enharmonically equivalent to a major sixth, the chord is enharmonically equivalent to (1, 3, 5, 6). The diminished seventh chord occurs as a leading-tone seventh chord in the harmonic minor scale. It typically has dominant function and contains two diminished fifths, which often resolve inwards. In most sheet music books, the notation Cdim or C denotes a diminished seventh chord with root C; but it may also happen, mostly in modern jazz books and some music theory literature, that Cdim or C denotes a diminished triad (more commonly denoted Cm5), while Cdim7 or C7 in these books denotes a diminished seventh chord (corresponding to Cm65). François-Joseph Fétis tuned the chord 10:12:14:17 (17-limit tuning). Analysis Music theorists have struggled over the centuries to explain the meaning and function of diminished seventh chords. Currently, two approaches are generally used. The less complex method treats the leading tone as the root of the chord and the other chord members as the third, fifth, and seventh of the chord, the same way other seventh chords are analyzed. The other method is to analyze the chord as an "incomplete dominant ninth", that is a ninth chord with its root on the dominant, whose root is missing or implied. A vii7 chord in the minor key (for example, in C minor, B–D–F–A) occurs naturally in the harmonic minor scale and is equivalent to the dominant 79 chord (G–B–D–F–A) without its root. This was already proposed by Arnold Schoenberg, and Walter Piston championed this analysis. Jazz guitarist Sal Salvador, and other jazz theorists, also advocated this view, rewriting chord charts to reflect this and supplying the "missing" root as part of their bass lines. The dominant ninth theory was questioned by Heinrich Schenker. He explained that although there is a kinship between all univalent