This week we continued working with concepts from the last two weeks, putting them together to look at the details of musical phrases. Remember, different analysts are looking for different things. There is more than one right answer.
Prolongation begins with the idea that T, P, and D are more stable or structural chords than any others. (This is why we relate other chords back to these three.) However, if we only wrote music with these three basic chords, it would get repetitive fairly quickly. If a function (such as T) is embellished in such a way that it is implied to last longer than the chord itself, we say it has been prolonged. There are 3 main ways of doing this: changing the bass pitch (inversion – covered last week), adding extra notes in upper voices (see below), and using other chords to extend the function’s influence (also below).
If the melody (or other upper voices in a texture) sounds pitches that are not any of the 3 or 4 associated with the current harmony we say these pitches are non-chord tones (NCTs). NCTs usually resolve by step to a pitch that is part of the harmony/chord (either the current harmony or the following one). There are specific names for approximately 12 types of NCTs, but we aren’t concerned with the names at the moment. Often we simply circle NCTs and then ignore them while we are doing a harmonic analysis.
Sometimes, NCTs contribute hugely to voice-leading in a way that is analytically interesting. Then it may be useful to track which NCTs are where. This can be done with arabic numerals, as we see here with an excerpt from Bach Well Tempered Clavier book 1 prelude in C major (mm. 24-27):
Starting in the second measure of the excerpt, we can follow the voice-leading of the 2 uppermost voices with the arabic superscripts.
When several NCTs appear simultaneously, they can form their own chord. Depending on the tempo and/or the level of detail you are interested in analyzing, it may be interesting to note each verticality as its own label. What follows will illustrate both the concept of levels and then prolongation. (Click to see larger version)
Depending on the performance, most listeners either perceive the dotted quarter (beat) level or the whole measure level as the primary unit of harmonic motion. If you, like me, focus only on about 1 chord per bar, the top analysis may be sufficient detail for you. However, the second analysis is more detailed, and shows inversions, added tones, and the cadential motion that I originally glossed over. Both analyses are correct, one merely has more details than the other.
There are at least 2 additional levels in just these four measures.
If you wanted to slow the tempo down and write a new variation at the new slow tempo, the sixteenth note chords in the first 2 measure might become relevant. These we normally ignore as NCTs, but when isolated do make up chords as well ( D5 and T, respectively).
The biggest level is the prolongation. Notice that the downbeat of m. 1 and m. 4 are the same. All the chords in between are said to have prolonged the tonic for 3 entire bars. We know that the prolongation is over because we have moved to a new functional area (P) so that the cadence can begin.
There are many types of common Tonic prolongations. The most basic are (T-D5-T3) and (T- D3-Tr) which then acquire more variations and additions to increase interest and variety.
Similar types can be found prolonging Predominant or Dominant. A famous Dominant prolongation is the Dominant pedal (like the the above Bach example), where the bass stays on scale degree 5 while many things flow above it.