Part II: Diatonic Materials, Units 5-8

Study Guide 4: The Subdominant Triad; Cadences; The Cadential Six-Four Chord

The Subdominant Triad (Units 5 and 6)

The subdominant chord is built on the fourth scale degree. A common tone can be maintained in connecting the subdominant to the tonic:

subdom1aux

The subdominant frequently functions as a dominant preparation chord. It progresses to V and rarely follows V. The tonic, subdominant, and dominant are often referred to as the primary triads. The basic progression of I-IV-V-I can form the basis of phrases and entire pieces. In connecting the subdominant to the dominant in root position, the three upper voices move downward to the nearest chord tone, in contrary motion to the ascending bass:

subdom1

Parallel fifths and octaves are avoided in strict part-writing, in order to preserve the independence of voices. Use contrary motion between upper voices and the bass to avoid this trouble in connecting IV with V:

subdom1bad

Notice that in moving from IV to V7, a common-tone can be maintained, as the doubled root of the IV becomes the seventh of the V7:

subdom2
 

See the video: The Subdominant Triad
 

Cadences (Unit 7)

Cadences are points of arrival at the endings of musical phrases. Cadences involving the tonic and dominant are fundamental elements of structure in tonal music.

  • perfect authentic cadence (P.A.C.) employs the progression V (or V7) to I, with the tonic note in the soprano of the I chord. Both chords must be in root position.
  • An imperfect authentic cadence (I.A.C.) employs the V (or V7) – I progression with the third or fifth scale degree in the soprano of the I chord.
  • half cadence employs a progression ending on V. It a harmonically open event, requiring continuation.
  • plagal cadence (P.C.) employs the progression IV-I. It often follows after an authentic cadence to indicate closure.

These cadence types are shown below. The deceptive cadence is covered in Study Guide 6.
 

The Cadential Tonic Six-Four Chord (Unit 8)

The tonic 6/4 chord is a triad in second inversion, arranged so that the fifth of the triad is in the bass. The interval of the fourth above the bass is dissonant in this context. Consequently, the tonic 6/4 is an unstable chord that requires resolution. The cadential tonic 6/4 chord usually immediately precedes the V or V7 at a cadence. It is considered to be a nonfunctional linear chord, serving to embellish the dominant. Linear chords are analyzed in brackets. The fifth of the tonic 6/4 chord, the tone in the bass, is doubled in four-part writing:

cad-six-four

This passage provides two similar phrases forming a parallel period. The first phrase ends in a half cadence; the second phrase ends the two phrases with a perfect authentic cadence. Both cadenes are prepared with the cadential tonic 6/4/ chord:

flute_andante

(The i6 and ii6 chords are covered in our next study guide, and in the textbook, Units 9 and 10.)

The imperfect authentic cadence has either the third or the fifth of the tonic chord in the soprano in the final chord:

imperfect

Here is one of the most recognizable examples of a plagal cadence, from Handel’s “Hallelujah Chorus”:

halelujah

(The first chord shown, the I6, is covered in our next study guide, and in the textbook, Unit 9.)
 

Audio Credits

Mozart, The Magic Flute. Musopen (public domain)

Handel, The Messiah. Monteverdi Choir, John Elliot Gardiner, conductor  community audio