Exploring Scale and Chord Relationships in Music

Music theory is rich with intriguing techniques that enhance musical composition and improvisation. One fascinating aspect involves playing a scale that does not strictly belong to the underlying chord. This concept is essential for understanding advanced harmony and improvisation techniques in jazz and beyond. Let's delve into the terminology, significance, and applications of this technique.

Polytonality and Scale Over Chord Techniques

When a scale is played over a chord, and the scale notes incorporate alterations that create tension against the chord, you are utilizing a technique often called polytonality or scale over chord technique. For example, playing an E major scale over a C major chord introduces alterations such as F#, A, and D#, which create tension due to their natural conflict with the C major chord's notes (C, E, G).

The term polytonality specifically applies when you deliberately create two or more tonal centers simultaneously, often for an extended duration. If the scale or chord alteration is brief or used to create interest in a specific phrase, it is not necessarily considered polytonality. Typically, the term is reserved for cases where multiple tonal centers are maintained throughout a piece or substantial section of music.

Within the jazz and contemporary music context, a similar approach is called upper structures. This refers to using additional scale notes that lie outside the basic chord's scale but blend harmonically with it. For instance, playing the first five notes of a D major scale over a C711 chord can create interesting tonal colors while maintaining a coherent harmonic basis.

Tonal Centers and Cadences

When transitioning between chords, music often relies on established cadences to establish and resolve tonal centers. In the key of E major, playing a C note can suggest a minor iv chord (Cmin7), which can be beautifully incorporated into a progression like A, Am, E, E7. In the key of C, an E note can function as a V7 of vi (E7), leading nicely into Am, C, as in the progression Dm, E7, Am, C.

These scales and chords are examples of upper structures, which involve using a scale that is not the primary scale of the chord. This technique adds depth and complexity, as the scale notes introduce alterations that create interesting tensions and resolutions. For example, playing the E major scale over a C major chord introduces an F# and a B note, which are not part of the C major scale but still create a harmonious relationship when played strategically.

Upper Structures in Detail

Understanding upper structures involves recognizing the underlying cadences and how they function in various keys. Below is a breakdown of the upper structures derived from the C major scale, which consists of seven chords:

I Cmaj7 - Tonic, stable and restful II Dmin7 - Subdominant, encouraging motion III Emin7 - Submediant, stability with motion IV Fmaj7 - Dominant, preparing for resolution V G7 - Dominant, strong and leading forward VI Amin7 - Submediant, stability with motion VII B-7b5 (VII7 b5) - Dual functioning, both subdominant and dominant VIII Cmaj7 - Tonic, stable and restful (same as I)

Each of these chords has a cadence function that influences its role in the progression. The tonic cadence (I, III, VI) provides stability and rest, making them suitable for upper structures. The subdominant cadence (II, IV, VII) encourages motion, making them useful for leading into stronger chords. The dual-functioning VII chord can act as a subdominant or dominant, offering versatility in its application.

Upper structures can be used to substitute or build upon these cadence functions. For example, the VI7 (Amin7) can act as a substitute for the V7 (G7) or the I7 (Cmaj7), creating unique harmonic textures and resolving tensions in new and interesting ways.

In summary, exploring scale and chord relationships through techniques like polytonality and upper structures enriches musical composition and improvisation. By understanding how these alterations and substitutions work, musicians can create more complex and nuanced harmonies, leading to more engaging and meaningful musical experiences.