Inmusic theory, harmonic rhythm, also known asharmonic tempo, is the rate at which thechords change (orprogress) in a musical composition, in relation to the rate of notes.[2] Thus a passage incommon time with a stream ofsixteenth notes and chord changes everymeasure has a slow harmonic rhythm and a fast surface or "musical" rhythm (16 notes per chord change), while a piece with a trickle ofhalf notes and chord changes twice a measure has a fast harmonic rhythm and a slow surface rhythm (1 note per chord change). Harmonic rhythm may be described as strong or weak.
According toWilliam Russo harmonic rhythm is, "theduration of each different chord...in a succession of chords."[3] According to Joseph Swain (2002 p. 4) harmonic rhythm, "is simply that perception ofrhythm that depends on changes in aspects ofharmony." According toWalter 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 theroot changes as they occur, reveals important and distinctive features affecting thestyle andtexture."[4]
Strong harmonic rhythm is characterized by strong root progressions and emphasis of root positions, weakcontrapuntal bass motion, strong rhythmic placement in the measure (especially downbeat), and relatively longer duration.[5]
"The 'fastness' or 'slowness' of harmonic rhythm is not absolute, but relative,"[6][self-published source] and thus 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 betweenBaroque music andClassical-period music is that the latter exhibits much more variety of harmonic rhythm, even though the harmony itself is less complex.
For example, thefirst prelude (BWV 846) fromJ. S. Bach'sThe Well-Tempered Clavier, illustrates a steady harmonic rhythm of onechord change per measure, although themelodic rhythm is much faster.
