In music theory, harmonic rhythm, also known as harmonic tempo is the rate at which the chords change. According to Joseph Swain (2002 p.4) it "is simply that perception of rhythm that depends on changes in aspects of harmony." According to Walter Piston (1944), "the rhythmic life contributed to music by means of the underlying changes of harmony. The pattern of the harmonic rhythm of a given piece of music, derived by noting the root changes as they occur, reveals important and distinctive features affecting the style and texture."
Harmonic rhythm is rarely notated or described exactly; rather, analysts compare the overall pace of harmonic rhythm from one piece to another, or the amount of variation of harmonic rhythm within a piece. For example, a key stylistic difference between Baroque music and Classical-period music is that the latter exhibits much more variety of harmonic rhythm, even though the harmony itself is less complex.
Alexander Scriabin's music features an increasingly slow harmonic rhythm beginning in his middle period.
Prelude no. 1 in C major Play (help·info) (BWV 846) from J. S. Bach's Well-Tempered Clavier illustrates the difference between melodic and harmonic rhythm: through a constant stream of sixteenth notes, Bach changes chords only once per measure.
- Piston, Walter (1944). Cited in Swain, Joseph P. (2002). Harmonic Rhythm: Analysis and Interpretation. ISBN 0-19-515087-2.