In music theory, planing is a harmonic technique where a chord or a tonal structure is repeated while shifting its pitch up or down by the same interval. This creates a sense of movement without changing the chord’s quality or shape. Planing is often used to add color and smooth transitions within a progression.

There are two common types of planing:

• Parallel planing (or exact planing): The entire chord, including all intervals, moves up or down maintaining the same shape and quality. For example, a C major chord moving up a whole step to a D major chord. This can create a dreamy, non-functional sound because traditional harmonic rules about tension and resolution are relaxed.
• Modal planing (or diatonic planing): The chord tones move within a particular scale or mode, preserving the harmonic context but adjusting intervals to fit the key. This form sounds more consonant and less ambiguous than parallel planing.

Planing is frequently found in jazz, impressionist music, and modern compositions. Composers like Claude Debussy used it to break away from classical tonal harmony, creating rich textures and fluid progressions. In pop and rock, planing can also contribute to smooth chord changes that feel organic and flowing.

Overall, planing works in harmony by moving chords uniformly up or down, creating motion through consistent intervallic motion rather than traditional functional harmony. This technique offers composers and performers a creative tool to explore new harmonic colors and effects.