The term “mode” as it applies to music can have different meanings that can cause confusion if you’re not aware of the alternate usages. In this section, we will clarify the way “modes” are discussed in this book and learn about the contexts in which other meanings appear.
Modes are discussed in this book in the context of music that is “tonal.” Songs that are tonal are based around a scale and use chords functionally in a way that establishes a home base (e.g., through cadencing). Jazz (depending on the era/school) integrates some of the same concepts from tonal music but is not bound by them. In jazz, the harmonic structure of a song is often much less rigid. There often isn’t a single home base chord, and the tonal center at any given time can be more ambiguous. As a result of these differences, the concept of “modes” as we’ve defined them doesn’t have the same meaning in these genres. Instead, a related (but not equivalent) concept of modes is used.
When jazz players improvise over a chord progression, the answer to the question, “what notes should I play to make my melody sound good?,” is very different than the answer in the context of the music we’ve been studying in this book. In tonal music, the answer is more straightforward. If you are not borrowing a chord or temporarily playing around with another home base with a secondary chord, you use the notes from the scale the song is based on.\n \n\n\npFor example, in a tonal song, if you’re in the key of C major, and you are playing a G7 chord (V⁷), the notes in your melody should be from the C major scale. If you are playing a emdm chord (ii), the notes in your melody should be from the C major scale. However, in jazz, a song might use a G7 chord without a strong sense of harmonic context at all, so a different method is needed to know which notes might sound good. This is where “modes” come in.
Many students learning to improvise today are taught a system called “chord-scale theory” to pick the notes in their melodies. This improvisation technique came out of a style of jazz (“modal jazz”) popularized by Miles Davis, John Coltrane, and others during the 1950s and 1960s.
Greatly simplified, in this system a different scale or “mode” is associated with a particular chord quality. “Modes” are just different scales that you learn to use for your melodies over different chords†. For example, students might be taught to play a mixolydian scale whenever they see a dominant seventh chord. Their melody would contain notes from the G mixolydian scale whenever they hear a G7 chord, for example. Likewise, when playing a C minor seventh chord, for example, they might be taught to play from the C dorian scale. Whenever the chord changes, a new scale or mode is used to define the notes of their improvised melody.
The upshot is that students of chord-scale theory have a different conception of what it means to play in a mode. For them, the mode is what scale you play over a particular chord. This contrasts with modes in a tonal context that imply all sorts of things about the structure of the overall piece, the way chords are used together, etc.
Both of these uses are equally valid ways of conceptualizing the musical genres for which they are appropriate. However, chord-scale theory has a lot of shortcomings if you try to use it for understanding tonal music (and conversely the functional harmony described in this book cannot explain much of what goes on in jazz). The biggest problem is that when “modes” in the chord-scale theory sense are used to analyze tonal music, they add a great deal of needless complexity. A song that could be explained very simply and elegantly with the functional harmony we’ve discussed in this series can become a mess of “modes” changing for every chord.
Most modern popular music is tonal and can be explained better with functional harmony. A lot of jazz has tonal elements for which this is true as well. No matter what musical style you’re interested in, however, knowing the principles of tonal music as discussed in this book is an important part of becoming a better musician and songwriter.
† Of course, to the extent that a jazz piece is incorporating tonal elements, knowing how the chords function can be extremely useful. Many beginning improvisation students make the mistake of memorizing a bunch of scales/modes to blindly play whenever they hear different chords without considering the harmonic context.