note is then the root of a dominant seventh chord. Diminished seventh chords may also be rooted on scale degrees other than the leading-tone, either as secondary function chords temporarily borrowed from other keys, or as appoggiatura chords: a chord rooted on the raised second scale degree (D–F–A–C in the key of C) acts as an appoggiatura to the tonic (C major) chord, and one rooted on the raised sixth scale degree (A–C–E–G in C major) acts as an appoggiatura to the dominant (G major) chord. Such chords however, having no leading tone in relation to the chords to which they resolve, cannot properly have a dominant function. They are therefore referred to commonly as non-dominant diminished seventh chords or common tone diminished seventh chords (see below). In jazz, the diminished seventh chord is often based on the scale degree (the flat mediant) and acts as a passing chord between the mediant triad (or first-inversion tonic triad) and the supertonic triad: in C major, this would be the chord progression E minor – E diminished – D minor. The chord, "plays no role in... jazz." The passing chord is used widely in Brazilian music such as choro, samba and bossa nova. Other functions Another common use of the chord is as a sharpened subdominant with diminished seventh chord. This is represented by the Roman notation iv7, but in classical music is more correctly represented as vii7/V, being a very common way for a composer to approach the dominant of any key. In the key of C, this is Fdim7. It is also a common chord in jazz and ragtime music. A common traditional jazz or Dixieland progression is IV–iv7–V7 (in C major: F–F7–G7). Another common usage of iv7 is often found in Gospel music and jazz progressions such as in the song "I Got Rhythm": In C: | C C/E | F Fdim7 | C/G A7 | Dm7 G7 | One variant of the supertonic seventh chord is the supertonic diminished seventh with the raised supertonic, which is enharmonically equivalent to the lowered third (in C: D = E). It may be used as a dominant substitute. A diminished seventh chord may function as a common-tone diminished seventh chord. In this role, a diminished seventh chord resolves to a major or dominant seventh chord whose root is one of the notes of the diminished seventh chord (common tone), the most