Why Certain Modes Fit on Certain Chords
Modes and Scales
The major scale is the foundation of Western music theory, and it has seven modes. Modes are essentially different scales that are derived from the same parent scale. Each mode has a different sequence of intervals, which gives it a unique sound and character.
The Melodic Minor Scale is another parent scale used frequently in music theory. Practicing Melodic Minor scales is essential as they have seven more modes that can be used to create chords and scales.
Let's take a closer look at one of the modes - the Lydian Dominant mode. This mode is derived from the fourth mode of the Melodic Minor scale. The Lydian Dominant mode is a dominant seventh chord with a sharp four, and it fits perfectly with chords such as B7#11.
Chords and Scales
Chords and scales are essentially the same thing. A chord consists of four notes - the root, third, fifth, and seventh. The upper extensions, such as the ninth, eleventh, and thirteenth, are just additional flavors or spices that give the chord a unique character.
The bottom four notes of a chord are known as functional harmony, and they tell you what the chord is doing and its purpose. The upper extensions are just additional notes that add flavor to the chord.
The magic of chords and scales is that the upper extensions - the ninth, eleventh, and thirteenth - are the other three notes of the scale. When we see a chord symbol that doesn't have the upper extensions written in, we have some ambiguity. This is where jazz musicians come in, and they can play different modes on that chord.
However, if the chord has the upper extensions written in, it's telling you what the scale is. For example, Ebm7(6/9) is telling us it's a Dorian mode. B7#11 is telling us we have a sharp four in the scale, and it's the Lydian Dominant mode.
Knowing the modes, scales, and chords can help you create unique sounds and compositions. Remember, chords and scales are essentially the same thing, and the upper extensions are the other three notes of the scale.