What defines modal jazz in relation to traditional harmony?

Modal jazz is characterized primarily by the absence of traditional functional harmony, which means it does not rely on established chord progressions that define the tonal center in the way that much of Western music does. Instead of progressing through a series of chords that often resolve in predictable ways (like moving from the tonic to the dominant, etc.), modal jazz focuses on modes—scales derived from a single tonic pitch that provide a more open, fluid structure for improvisation.

This approach allows musicians to explore melodic ideas over static harmonies or a simple progression of modes, giving greater freedom for improvisation. The emphasis is on the use of modes rather than on chasing changing chords, thus enabling musicians to create complex and rich textures without the constraints of conventional harmonic movement.

In contrast, the other options either imply a reliance on traditional progression or adherence to strict scales, both of which do not accurately capture the essence of modal jazz. The focus of modal jazz is on the exploration of melody and tonal color rather than adherence to traditional harmonic rules.