Music 232 ð Diatonic Triads, Principles of Voice Leading

Week of 09/08/97



Diatonic Triads

Triads and seventh chords in tonal music are analyzed by using roman numerals, indicating the scale degree that is the root of the chord.

ð Types of triads and seventh chords in Major and minor modes
TRIADS
Major I ii iii IV V vi viio
minor i iio III iv V VI viio
SEVENTH CHORDS
Major IM7 ii7 iii7 IVM7 V7 vi7 viio7
minor i7 iio7 IIIM7 IV7 V7 VIM7 viio7


NOTE: The roots of the triads and seventh chords in these tables all conform to the harmonic minor scale. This is not necessarily the case with other chord members, who may may be affected by the variability of scales-degrees 6 and 7 in the minor mode.


Principles of Voice Leading

ð Grammar of tonal music:
Chords selected (ãharmonic progressionä)
Chords connected (ãvoice-leadingä)

ð Voice leading: the ways in which chords are produced by the motions of individual musical lines.

ð Melodic line
Procedures for effective melodic writing (vocal style):

1. Rhythm: Simple, most durations equal or longer to duration of the beat. Final
note on a strong beat.
2. Harmony: Every melody note belongs to the chord that harmonizes it.
3. Contour: Mostly conjunct (e.g. stepwise) motion. A single focal point (e.g.
highest note). Simple, smooth, but nteresting ãcurveä.
4. Leaps:

a) No augmented intervals, melodic 7ths or intervals larger than the octave.
Diminished intervals OK if melody changes direction by step immediately
after.
b) Intervals larger than a P4 approached are approached and left in opposite
directions.
c) Small leaps in the same directions must outline a triad.

5. Tendency tones:

a) Scale degree 7 to s.d. 1, except descending 1,7,6,5 lines
b) Scale degreee 4 often moves to s.d. 3


For further information about melodic writing: see class reference materials, ãAn Introduction to Tonal Melodyä


Notating Chords

ð Notation:
The method or methods used for writing down music. A fully developed system of notation must be designed so as to indicate clearly and completely the two main properties of musical sound: pitch and rhythm.

ð Musical Score:
A ãblueprintä where the composerâs ideas are presented for interpretation.
Full score: all parts (instrumental, vocal) are notated on individual staves
Reduced score: Only essential material is notated in as few staves as possible.

Four-part harmony (ãChorale-styleä, or ãSATBä) exercises, compositions are notated on two staves (reduced score), wiht the voices distributed as follows:

Voice

Abbreviation

Staff

Clef

Stem direction

Soprano

S

Top

Treble

Up

Alto

A

Top

Treble

Down

Tenor

T

Bottom

Bass

Up

Bass

B

Bottom

Bass

Down



ð Ranges of the voices:





ð Voicing a triad: how the voices in a single chord are to be spaced.

Open structure: an octave or more between S and T
Closed structure: less than an octavce between S and T


ð General conventions concerning spacing:

1. No part should cross above S or below B
2. All adjacent upper parts (SAT) should be kept within an octave of each other


ð Voice movement.

- Similar: (voices move in the same direction)
- Contrary: (voices move in opposite direction)
- Oblique: (one voice moves, the other remains stationary)
- Parallel: (voices move in the same direction by the same interval)


Each individual voice must mantain its relative independence. Excessive paralell motion promotes a lack of independence in the voices, therefore a variety of voice movement options should be present.

ð Parallels fifths and octaves: Avoided.
The P5 and P8 are the most stable of all intervals, and to link two voices through parallel motion at such intervals interferes with our perceiving each voice independently.

ð Consecutive fifths and octaves: Also avoided.
ð Unequal fifths (e.g. P5öo5): avoided.
ð Direct (or hidden) fifths and octaves: avoided between outer voices,
except when S moves by step.

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