Uses of the Chordal Skip.
The terms chordal skip and arpeggio are interchangeable, although “arpeggio” tends to refer to an extended broken chord rather than to a single skip. They can help intensify rhythmic activity (a) and break up parallel 5ths and octaves (b and c). In addition, arpeggiated motions can improve melodic lines by varying a prevailing stepwise movement (d), by subdividing a large leap into smaller ones (e), or by introducing stepwise motion, especially in the bass (f).
Arpeggiation with Non-chord tones
The process of arpeggiation becomes more complex when arpeggios make reference to nonchord tones. A non-chord tone is any note that does not form part of the chord. The use of these in arpeggio patterns is very effective because they are capable of enhancing the melodic interest of the arpeggio.
There are a certain number of generic types of non-chord tones that are extremely useful to know when you are writing arpeggio patterns. One of the most important of these is the passing note. A passing note is the note between two chordal tones that are a third apart. Occurring on a rhythmically weak part of the bar and safely nestled between two chordal tones, the passing note’s use provides melodic interest but does not in itself affect the harmony.
Another important non-chord tone is the returning tone. The characteristic feature of the returning tone is that the chord tone rises or falls to the non-chord tone and then immediately returns to it.
Using Non-Chord Tones
The principle behind these generic figures is that they are melody notes that do not disturb the harmony. As long as the harmony is sufficiently referenced, you can exercise freedom in where you place these non-chord tones.
Steps in an Arpeggio
In addition to non-chord tones, you must think carefully about the number of steps in an arpeggio. Ordinarily, arpeggios are in four, eight, sixteen, or thirty-two steps, which means that the arpeggio is in sync with the bar. However, you can obtain amazing effects with step numbers out of sync with the bar. Here again, there are a number of generic types that have found their primary application in various styles of dance music. These include five-step, seven-step, and eleven-step patterns.
The beauty of these is that because the number of steps is odd, different notes of the arpeggio are highlighted on the strong points of the measure. This is a sort of wheels-within-wheels effect that generates inner melodies in addition to the arpeggio.