More TwoVoice Writing

1
More Two-Voice Writing

• Double Counterpoint and Structure

2
Double Counterpoint

• In Double Counterpoint, aka Invertible
  Counterpoint, the upper and lower voices can
  exchange lines.
• This device is much more common in Baroque
  fugues.
• Composers in this period tend to write a new
  counterpoint for a reentry.
• The composer must be aware of how the interval
  changes when inverted.
• The proper procedure must be used if a consonance
  inverts to a dissonance.

3
Double Counterpoint

• Double Counterpoint at the octave retains the
  consonant and dissonant properties of the
  intervals except for the 5th -- which becomes a
  4th.
• Therefore all 5ths must be treated as passing
  tones, suspensions or other dissonance.
• Double Counterpoint at the 10th is rare.
• Similar motion in 3rds and 6ths can cause
  problems because they invert to 8vas and 5ths.

4
Double Counterpoint

• Double Counterpoint at the 12th is the most
  common.
• The 2-3 inverts to a 4-3.
• The main problem interval is the 6th which
  inverts to a 7th.
• It is often better to transpose the pitch level
  of both parts.
• The magic number is one more than the mode of
  inversion because the unison is a 1 not a 0.

5
Structure

• Musical structure is determined by the text.
• The text is partitioned into phrases.
• Each phrase is given a different thematic idea
  which is usually presented in imitation.
• After the imitation, the phrase continues in free
  counterpoint.
• Each phrase usually ends with a cadence.
• Any reentries of the original motive are
  accompanied by the original text.

6
Structure

• Interior phrases tend to be more rhythmically
  active than the opening phrase.
• They can begin with a value as small as a minim.
• They usually commence on a weak beat.
• The previous phase has cadenced on a strong beat
  and this helps maintain a flow.

7
Structure

• Interior phrases tend to have more reentries.
• Reentries usually happen after a rest of one or
  two beats.
• A theme can reenter any number of times.
• Text setting, note values, and at least first 4
  pitches of the theme are used in a reentry.
• Although if it starts with a dotted or non-dotted
  semibreve it may shorten the duration by a minim.