The next component of scale theory is the distinction of each degree of a scale or chord. Just as in previous examples, beginning on the 5th degree or 6th degree effects the perfect fifth and relative minor respectively – so will beginning on any degree of a scale invoke a mode (the displaced starting point of a scale). For instance, if you were to take a C Major scale (C, D, E, F, G, A, and B) and displace the starting point from the root of C to the 2nd degree (without changing the intervals), you would begin and end on a D. In other words: D, E, F, G, A, B, C, and D.
The modes, also known as “chord scales” are simply formed and played by beginning on a note in a particular scale (root, 2nd, 3rd, 4th, 5th, 6,th and 7th).
Since there are seven degrees in a scale, there is a corresponding mode for each one. The first mode, beginning on the root, is called Ionian. Each of these modes provides an array of possibilities in composition of rhythms, chords, and, of course, solos.
The next mode begins on the 2nd degree, and is called the Dorian. This mode is commonly found in jazz (as is almost every mode) and jazz-rock. This mode sounds much like a natural minor, with the 6th degree raised.
The Phrygian mode, is effected by beginning on the 3rd degree and is an insinuation of flamenco and alternative rock. It is also found throughout blues and blues rock, in 3rd chord dyads (a two note chord consisting of the root and 3rd).
The Lydian mode, found on the 4th degree, sounds much like a major scale. This mode is prevalent in jazz soloing and again in blues, blues-rock and rock (likewise, in dyad chords – where the root is coupled with the 4th degree).
The Mixolydian mode is invoked by starting at the 5th degree, and sounds like a major scale. This mode will be encountered heavily in every type of rock, blues, jazz, folk, and just about any genre one could possibly name. The reason being, that when coupled with the root, this forms the ever popular “power chord”.
The mode effected by the 6th degree, the Aeolian, invokes the relative minor of the root. The fundamental distinction between the major (also known as the Ionian) and the minor is the tonal quality. This mode is not as common as the preceding 5th degree, but can be found in a few different genres –- such as jazz, which of course, employs this mode as does rock.
The last mode, the Locrian, is the most discordant of the all the modes, and is not typically found in music as a purposely placed effect, but more so an unintentional phenomenon. Though it is used in jazz as to solo over half-diminished minor chords, it does not serve an express purpose or invoke a harmonization like that of the other modes and is mostly happenstance.
The best way to grasp the concept of modes is to think about baseball or softball diamond. If you were to run the bases freely, it doesnt matter where you begin. The bases never change position, just where you choose to start and stop. The same holds true for modes. No matter on which note you begin on a C Major scale, it remains a C Major scale, you’re just beginning and ending the scale on a note other than C.