The Architecture of Music


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Tonality and Chord Progressions

Dorian Modes

By Ethan Lustig, MA Music Theory

When you make music using a scale, you are limiting the pitches to a particular collection. This is not “limitation” in a bad way: if anything, it means that your piece (or, for pieces that shift collections, a portion of your piece) is well-organized and clear. In fact, the vast majority of music, from around the globe and throughout history, stays within one scale, and even within one particular mode of that scale. In other words, most songs do not use all 12 possible pitches (although, as we will soon see, the Chromatic Scale does this and is very difficult and complex to play). When a song is in a particular mode, usually the melody, bass line, and chord progression will circle around, and point to, one pitch more strongly than the others. This creates a sense of “tonality”, the property of having a pitch that serves as a gravitational center, a home base. This pitch is called the tonic, or the key note of the mode the song is based on. The tonic is the most stable pitch, with the most repose and the least dissonance. Often the piece (or phrase) will end on this pitch.

Consider music written in, for instance, Suspended Pentatonic (mode I) vs. Minor Pentatonic (mode IV) vs. Major Pentatonic (mode V). If you start all three modes on A, in A Suspended Pentatonic, mode I will have B as its second pitch, whereas in A Minor Pentatonic (mode IV) begins with A, then C, lacking a B entirely; and A Major Pentatonic (mode V) has C#, which is absent in the other two modes. And also, the key notes of each scale will differ: to start mode I on A means the key note of the scale is A; to start mode IV on A means the key note of the scale is D; and to start mode V on A means the key note of the scale is B (see quick scale reference chart on page 245 in the book). Yet in all three cases, the tonic or key note of the mode is said to be A. It is important to understand the difference between the tonic/key note of the mode and the key note of the scale.

You can use chords to establish and reinforce the tonality of a song. The most typical and basic type of chord that you can use to convey a tonality and make chord progressions is called a triad. A triad has three notes stacked on top of each other, a major or minor third apart. For example, A C# E (4 3 5, aka. maj3 or the “major triad”), A C E (3 4 5, aka. min3 or the “minor triad”), A C D# (3 3 6, aka. the diminished triad), and A C# F (4 4 4, aka. the augmented triad) are the four most compact triads that you can build above the note A.

Some scales work better than others for the purpose of building triads. The Dorian scale (and its modes) is excellent for building triads, and thus for creating a tonality using chord progressions of triads. This is because of its interval formula (2 1 2 2 2 1 2), which allows for 3s and 4s (the two types of intervals of a third: minor third and major third, respectively). In fact, 3 or 4 can be generated via addition of every adjacent pair within its formula (2 + 1 = 3, 1 + 2 = 3, 2 + 2 = 4, etc). As a result, you can build a triad on every member of the Dorian scale, as can be seen on the following page. And because the modes of the Dorian Scale are simply rotations of the same formula (they simply move the numbers to the left, rather than rearranging the ordering), this principle applies to all of its modes as well. The Suspended Pentatonic scale, meanwhile, does not allow for plentiful triad-building, because the Suspended Pentatonic’s formula (2 3 2 3 2) does not allow for enough 3s and 4s to build a triad from each of its members. As can be seen on page 11 of this section, maj3 can only be made with mode V (Major Pentatonic), and min3 can only be made with mode IV (Minor Pentatonic), but no other triad can be made from the other modes.