MUS 112 Study Guide N (Chapter 14)

Submediant & Mediant Triads

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  1. The submediant triad (vi or VI), though occurring less frequently than those previously studied, is the most versatile in terms of those triads to which it can relate.

In progressing toward the tonic, the submediant triad is commonly followed by the supertonic (ii, iio), subdominant (IV, iv) and dominant (V) harmonies.

The progression V-vi or V-VI is quite common.  Because the expectation of V moving to I is so compelling, V to the submediant chord is commonly called deceptive; at a cadence the progression is called a deceptive cadence.

  1. The mediant triad (iii or III) is, in major, the furthest away from tonic in the progression of root movement by fifth.  It is used considerably less than other triads.

The mediant triad usually progresses to the submediant (iii-vi, III-VI) or to a subdominant function (iii-IV or ii6, III-iv or iio6).  Note that in both IV and ii6 (iv and iio6), the bass is the subdominant note.

Probably the most frequent use of the mediant is in a progression of three triads vi-iii-IV (VI-III-iv).  The progression vi-iii is infrequent without the following IV or iv.

  1. Root Movement by Downward Thirds:  With the inclusion of the submediant triad, it is possible to construct a harmonic pattern based on root movement by thirds.  Of all the possible movements by thirds, the progression I-vi-IV-ii (in whole or in part) is common.  In vi- ii6, the bass movement down a third produces an aural effect of root movement down a third, as though it were vi-IV.  The progression IV-ii is also possible.  V-iii is uncommon (deceptive).

  1. Root Movement by Downwards Fifths:  The most useful progression from the submediant is to the supertonic, either in root position or in first inversion.  Progression from iii to vi should be common, considering the root movement by fifth, yet it is far less common than root movement by second, iii-IV.

  1. Root Movement by Seconds–the Deceptive Cadence:  The deceptive cadence (V-vi) is one of the most dramatic of any individual chord progression, for reasons stated earlier.  This progression may appear equally as well within the phrase.  Combined with nonharmonic tones, it can be particularly effective.

The most common use of the mediant triad, iii-IV, is particularly effective in harmonizing the descending scale line 8 7 6 5.  The roots of I-iii-iv-V in the bass produce a line in contrary motion to the melody.

  1. The vi-iii-IV Progression: in minor, VI-III-iv.  Having vi precede iii is uncommon unless IV follows.  Substitution of ii6 or iio6 for IV after the mediant triad is possible because both progress to V and they have the same bass note.

  1. Inversions of the Submediant and Mediant Triads:  Submediant and mediant triads are infrequent in first inversion and rare in second inversion.  Each of the triads usually appears in first inversion only when the root of the preceding triad is the same bass note as the first-inversion note.  There are just two practical possibilities: I-vi6 and V-iii6.

  1. Writing the Submediant and Mediant Triads:  Most progressions in root position can be written using conventional procedures.  When either triad is inverted, use the conventional procedure for approaching and resolving the doubled tone (contrary or oblique motion, if possible).

When roots are a second apart and the soprano and bass move in the same direction, as in V-vi or vi-V, the conventional procedure will not work because parallel 5ths, 8ths, and/or augmented 2nds usually result.  In this situation: double the third in the submediant triad.  This procedure can be used in similar situations where use of conventional procedures is awkward or impossible.  Doubling the third is especially effective when the doubled note is the tonic, subdominant or dominant note of the key.  When the soprano and bass move in contrary motion, write the upper three voices so they move in contrary motion to the bass.

When roots are a third apart the chords have two tones in common.  Usually it is necessary only to hold these two tones and move the other voices by step.  This procedure is useful in the progression I-iii (i-III), I-vi (i-VI), IV-ii and vi-IV (VI-iv).

The mediant triad is used infrequently in inversion.

Should the melody line skip a third or more when the roots move by third, there is no conventional procedure.  Simply make sure that there are no parallels and that the voices are in range.

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