Describe the role and application of pedal points and ostinatos in jazz arranging, providing examples of their use in well-known arrangements.

Pedal points and ostinatos are powerful arranging techniques used in jazz to create harmonic stability, rhythmic drive, and a sense of continuity. While both involve a repeating element, they differ in their nature and application. A pedal point is a sustained or repeated note, typically in the bass, that remains constant while the harmony above it changes. An ostinato, on the other hand, is a short melodic or rhythmic pattern that is repeated persistently throughout a section of music, and can be placed in any voice. These techniques can be combined or used separately to create a wide range of musical effects. Pedal points create a sense of harmonic tension and release by providing a constant reference point while the harmony moves around it. Usually, the pedal note is a tonic, dominant, or subdominant note in a key. As the chords change above the pedal point, it creates a unique and colorful harmonic landscape. The use of a tonic pedal creates a feeling of stability and can help reinforce the sense of key. When a dominant pedal is used, a sense of unresolved tension is created, making the resolution to the tonic more powerful. The subdominant pedal is less common but can create a softer, more reflective harmonic environment. The harmonic interest is generated by the contrast between the unchanging pedal note and the changing chords above it. For example, if a C pedal is placed in the bass while a progression like Dm7-G7-Cmaj7 moves above it, the C will sometimes be a chord tone of the current chord and sometimes not. The fact that it is not a chord tone during the Dm7 and G7 gives the chord a particular unique sound. It adds a layer of depth and harmonic complexity. Pedal points are ofte....