A chord progression is a group of vertically-placed, simultaneously-played melodies. A chord's vertical placement results from the smooth direction of each of the lines. Traditional notation often hinders the perception of the linear aspects of a chord progression. Play the example above several times and try to correlate both the horizontal and vertical aspects of the progression with your ears and eyes.
After seeing and hearing the example as it occurs in real time, you will see its traditional notation in Example A below. Although the linear aspects of the progression become less apparent, the concept of watching and listening for the direction of individual voices in a chord progression is important in all musicmaking!
EXAMPLE TRADITIONAL NOTATION
Chord voicing is a reliable indicator of style. Left-hand piano voicings, for instance, can provide a reliable harmonic blueprint for the entire jazz tradition. In Example B below, the C7 chord is portrayed in various jazz styles and examples of variations of each style can be heard by pushing the "play" buttons.
EXAMPLE . HISTORICAL LEFT HAND PIANO VOICINGS
1. Ragtime and stride piano left-hand voicings often are defined, as notated above, with octaves on the root on beat one, on the fifth on beat 3, with the same voicing of the chord on beats 2 and 4. In reality, however, the early stride pianists also played left-hand octave melodies, chord melodies (one of the notes of the chord, usually the highest, supplying a countermelody with a line in the right hand, meter changes (usually from 2/4 to 3/4), and complicated rhythm and accents--all which require advanced control and techniques. 2. BoogieWoogie patterns are usually played over the 12-bar blues. In contrast to stride playing, the boogie-woogie pianist maintains the same left-hand shuffle rhythm pattern (played on the I, IV and V chords of the blues progression) while showing the independence between the two hands in managing intricate interlocking accents and rhythms. The upper voice of the left-hand pattern is a good example of step-wise voice leading providing the harmonic momentum within the same chord--as the 5th (G) moves through the 6th (A) up to the 7th(Bb) and back down again of the C7 chord.
3. During the bebop period, beginning in the 1940s, the right hand provided harmonic sophistication by running extensions of the chord members as part of the melodic line. The left hand provided punctuation, as much as a harmonic backdrop. (The harmonies also changed much more frequently during this period.) The roots of the left-hand chords began to be left out on occasion, but the resolution of 3rd and 7th of the dominant 7th chord usually were handled carefully in any voicing toward the tonic. (For example, if an F Major chord were to appear in the next measure, the E and Bb of the C7 chord above, would most likely resolve to an F and A.)
4. Voicings gradually became more harmonically ambiguous. After adding extensions and alterations, and by leaving out the chords' roots, pianists soon found that a certain "sound" could be obtained by stacking specific interval combinations. (In fact, for some players the term, "voicing", implies only a specific relationship of vertically-stacked intervals rather than the "voice leading" of individual chord members with both horizontal and vertical implications.) A dominant 7th chord, for example, can be voiced by stacking a tritone plus a perfect fourth above either the 3rd or the 7th of the harmony. Thus, the first chord in the example is built on the third of the C7 chord," E", and the next chord is built on the 7th, "Bb". The altered extension in the first chord, "Eb", (enharmonically spelled as "D#" in a C7 chord extension) sounds like a sharped 9th and the "A" in the 2nd chord is the 13th of the C7 chord.
5. Quartal harmonies, stacked fourths, often occur in modal compositions. Thus, a C7 chord is entirely appropriate for a composition written in C mixolydian. However, it would be played as a sus. 4, thus leaving out the 3rd and omitting the specific tension of the tritone (E to Bb) for the desired ambiguity of quartal harmony. The example above uses pitches from an extended C7 chord, but in no way emphasizes either the root of the dominant 7th quality. With a bass player playing pitches based around C, the notes in the example above can be heard as being derived from C but (depending on the bass player) could just as easily be interpreted as belonging to A or D dorian. Voice leading in this context relies on the frequent stepwise motion of the stacked chords.