The analyses on this website are based on the Schenkerian System. It is really nothing more than a way of explaining that which most musicians and music aficionados know instinctively -how a given harmonic progression works, and why certain sequences of chords sound more natural than others. In short, Schenkerian analysis uses letters, words, and numbers to clarify and quantify that of which the trained ear is already aware.
To better understand the notation, think of the key of “C” on a piano and the corresponding three-note chords you could play by pressing every other white key. A “C, E, G” is a major “I” chord, because built on the first note of the scale. “D, F, A” is minor, and built on the second note, so it becomes an “ii” chord - and so forth. ”G, D, B” is, of course, a V chord. If you add a fourth note, “F”, it becomes a “seventh” chord, notated “V7” because we added F, the seventh note up from “G”.
In the Western European tonal tradition, a given chord has a strong tendency to either follow or precede certain other chords. The most powerful and important harmonic sequence is that which every first-year theory student learns as I -V7 -I, or “tonic -dominant -tonic.” In the key of C then, this would be C -G7 -C. According to Heinrich Schenker, virtually every piece of tonal music written in the past five hundred years boils down to the I -V7 -I sequence.
When most Westerners hear the V7 chord, usually the next thing they expect to hear is I, which is usually what happens, often with some other chords in between. If a V7 is followed by anything else, it’s usually called a “deceptive” resolution, because the listener has been “deceived” into expecting to hear one thing, but actually hears something else.
Schenker’s analysis system studies the various routes, detours, and side-journeys of the tonic key on its way to the dominant key and back -looking at these not only from a chord-to-chord perspective but a linear perspective as well. In other words, how individual voices move from one note to the next, and how these work with other voices to create harmonic progressions.
The JazzStandards.com analyses assume a basic knowledge of elementary music theory, although some explanations are included along the way that can be followed with any experience with music. When introducing more advanced concepts such as the “augmented sixth” (+6) and “Neapolitan sixth” (N6), I have tried to give relatively simple examples. It should be understood that my own use of these terms does not necessarily correspond to “textbook” theory -they are simply labels I have used for convenience, based on their sound and harmonic function. (Generally speaking, an “augmented sixth,” written “+6” and usually labeled as “Ger,” “Fr” or “It,” is a chord that is a half-step higher than V7. It usually resolves to V7, functioning as a substitution for the secondary dominant, or V7/V. An example would be Ab7 - G7 in the key of C. A “Neapolitan sixth,” or N6 chord, is a tri-tone substitution for V7, being a half-step higher than the tonic, and resolving to I, and would be Db -C.)
K. J. McElrath, Musicologist for JazzStandards.com