The use of the secondary dominant as a harmonic device
A secondary dominant is a move to 'the dominant of degrees other than the tonic.' (New Harvard Dictionary of Music)
In Duke Ellington's, 'A Gypsy Without a Song,' there is an obvious use of the secondary dominant in the development section. In this section, the piece moves from the tonic key of C major used in the exposition section, to the dominant key of G major. In the development section we also see the frequent use of the F7 chord and the D7 chord. In the context of G major, these chords can be seen as secondary dominants. F is the dominant of B, which is the mediant of G. If one then takes the change from G major to F7 as a temporary modulation, then the
D9 can be seen as a further secondary dominant. In the key of F, D is the dominant of G, the supertonic. Furthermore, the use of the note Eb in the F7 and D9 chords, adds to the sense that this is the development section by giving it a more minor sound. This provides a contrast to the major sound of the exposition section. In the recapitulation, the return to C major is marked by the abandonment of the Eb.
In Duke Ellington's, 'A Gypsy Without a Song,' there is an obvious use of the secondary dominant in the development section. In this section, the piece moves from the tonic key of C major used in the exposition section, to the dominant key of G major. In the development section we also see the frequent use of the F7 chord and the D7 chord. In the context of G major, these chords can be seen as secondary dominants. F is the dominant of B, which is the mediant of G. If one then takes the change from G major to F7 as a temporary modulation, then the
D9 can be seen as a further secondary dominant. In the key of F, D is the dominant of G, the supertonic. Furthermore, the use of the note Eb in the F7 and D9 chords, adds to the sense that this is the development section by giving it a more minor sound. This provides a contrast to the major sound of the exposition section. In the recapitulation, the return to C major is marked by the abandonment of the Eb.
In 'Doctor Gradus ad Parnassum,' Debussy also makes use of the secondary dominant, particularly in the development section as found in the Duke Ellington. Here we see the frequent use of an emphasis of the notes A and Ab. A is the dominant of D, which is the supertonic of the tonic key of C. Db is also an important note in the development section which relates to the Ab in the same way.
An example of the use of the A chord can be seen in the transition between the exposition and development sections, in bars 33 to 36. Here the piece modulates from C major to the key of Bb major, with the note G being heard in bars 34 and 35, in preparation for the start of the development proper in bar 37. Unusually, Debussy chooses to continue the note A in the left-hand emphasising its importance.
A further example of the importance of the A chord can be seen just after bars 43 and 44. In these bars, the A chord becomes an Ab chord, which is important for the lead back into the recapitulation. In bar 45, the Ab chord (bV of D) is a pedal note that is sustained and accompanied by the dominant of C (the note G) in the left-hand. In this way, the resolution from Db to C major is made possible thanks to the A chord representing a secondary dominant of C.