Describe a common chord substitution technique that replaces a dominant chord (V) to create a smoother, more sophisticated harmonic progression.

A common chord substitution technique that replaces a dominant chord (V) to create a smoother, more sophisticated harmonic progression is using the tritone substitution. A dominant chord (V) is a chord built on the fifth degree of a scale and has a strong tendency to resolve to the tonic (I) chord due to the presence of a tritone interval between its third and seventh degrees. The tritone substitution replaces the dominant (V) chord with a dominant chord built on a note a tritone away. In the key of C major, the dominant chord is G7 (G-B-D-F), which resolves strongly to C major (C-E-G). The tritone substitution of G7 would be Db7 (Db-F-Ab-Cb). The notes B and F in the G7 chord form a tritone. The notes F and Cb (enharmonically B) in the Db7 chord also form a tritone. Since the tritone remains, the substituted chord still retains a strong pull to the tonic, but the movement to the tonic is harmonically richer and more unexpected. The resulting bass movement from Db to C creates a chromatic stepwise motion, which is considered smoother than the perfect fifth movement from G to C. This technique adds harmonic color and complexity while maintaining a strong sense of resolution. The tritone substitution creates a more interesting and jazzy sound, commonly used to add sophistication to chord progressions.