IV - ♯iioo7 - I

The ♯iio^o7 is a diminished-seventh chord rooted on the raised supertonic (♯2). It occurs with some frequency in the pop music of the late ‘50s and early ‘60s, regularly progressing to I, with its root (♯2) moving up a half-step to the third of the tonic chord (3), its third (♯4) moving up a half-step to the fifth of the tonic chord (5), its fifth (6) descending by whole step to the fifth of the tonic chord (5), and its seventh (1) carried over as the root of the tonic chord. 

 


It’s the carrying over of  the seventh of the diminished-seventh chord as the root of the succeeding chord (represented here in the soprano voice) that gives rise to the term ‘common-tone resolution’ for a progression of this sort. It is to be distinguished from the more classical resolution in which the root of a diminished-seventh chord moves up a half-step to the root of the succeeding chord, as in the soprano voice below:  

 

Note how much more final this viio^o7 - I resolution sounds, even with tonic chord inverted. The ♯iio^o7 - I resolution, by contrast, sounds incomplete and for that reason is rarely used in a final cadence. 

In pop music of the period ♯iio^o7 is more often than not preceded by IV, making for a stock IV - ♯iio^o7 - I progression. 

 This combination of chords implies a 4 - ♯4 - 5 melodic line, characteristically heard in the bass, as above, so that the tonic chord occurs in its unstable second inversion, with a strong propensity to move onward.

An early example of this harmonic structure is found in Bessie Smith’s 1929 recording of Jimmy Cox’s Nobody Knows You When You’re Down And Out:
 

F                  D♯dim^o7/F♯    C/G                   A⁷  

     It’s mighty strange,                  without a doubt,

IV                  ♯iio^o7              I                     V⁷/ii

   D⁹                                                  G⁷                  C

          Nobody knows you when you      down and out
V⁹/V                                                V⁷                   I




Here the IV chord begins a 4-beat hypermeasure that has ♯iio^o7 falling on the unnaccented second hyperbeat (appropriately accompanying the word ‘strange’) and I falling on the accented third hyperbeat. A chromatically altered submediant chord (VI⁷ = V⁷/ii) fills out the fourth hyperbeat, initiating a V⁷/ii - V⁷/V - V⁷ - I, catapentic chain that runs through the next hypermeasure and ends in an authentic cadence. 

The V⁷/ii - V⁷/V - V⁷ - I progression makes a particularly nice complement to the IV - ♯iio^o7 - I progression, balancing its chromatically ascending 4 -♯4 - 5 line (heard in the bass voice below) with a chromatically descending 5 - ♯4 - ♮4 - 3 line (heard in the alto voice):