Jan. 10, 2017

Segmentation

The first segments of an orange when it's peeled, especially when someone is hungry, seem to be far more interesting than the rest of the orange (photo).
In just the same way, when a musical theme is divided into 2 or more segments, the 1st of these segments is of prime interest and can be reiterated to help generate excitement going into the coda; the remainder of the segments can also be worked to help spin out additional material for a bridge or development section.
This compositional tool is called segmentation.
In this technique the entire theme is divided into several segments each one measure long; the rhythmic figure found in each measure is then worked as a short motif to help create bridge passages or developments.
The score for Prelude Internationale Op. 5 exemplifies how this works [See menu bar, Free Stuff, 10 Pieces for the Organ Op. 1-9].
As the coda of a work is approached segmentation is also often employed.
In this situation the 1st phrase of the theme is divided in half, then the 1st half of that phrase is reiterated.
After this, the 1st half of this 1st phrase is divided in half again, and the 1st half of that is reiterated.
These 1st few notes are then repeated as a short motif over and over, thus pounding them into the listener's ears and raising the level of excitement in the closing measures.
Sometimes these 1st few notes are divided in half yet again, down to maybe only a couple of notes which are then reiterated until there's nothing left to reiterate; here the front end of the theme winds up fresh squeezed until all the juice in it is used up.
The c minor Op. 11 Prelude, the a minor Op. 25 Prelude, the F Major Op. 19 Toccata, and the b minor Fugue Op. 26 exemplify how this method of segmenting a theme works in a coda [See menu bar, Free Stuff].
This technique can also be applied in other imaginative ways.
For example, in working a fugue, just the "tail" (last few notes) of the subject might be derived by segmentation and reiterated in the top line after the stretto section to heighten the interest during the final measures.
For an example of how this works, the score for the A Major "jig" Fugue Op. 13 posted on this web site may be consulted [See menu bar, Free Stuff].
Not every theme lends itself to this treatment, and it should be used sparingly, but when it can be worked into the music it's a very effective device and has a place among several other time-honored compositional tools.