In music theory

Music theory

Music theory is the study of how music works. It examines the language and notation of music. It seeks to identify patterns and structures in composers' techniques across or within genres, styles, or historical periods...

, harmonic rhythm, also known as harmonic tempo is the rate at which the chords

Chord (music)

A chord in music is any harmonic set of two–three or more notes that is heard as if sounding simultaneously. These need not actually be played together: arpeggios and broken chords may for many practical and theoretical purposes be understood as chords...

 change. According to Joseph Swain (2002 p.4) it "is simply that perception of rhythm

Rhythm

Rhythm may be generally defined as a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions." This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or...

 that depends on changes in aspects of harmony." According to Walter Piston

Walter Piston

Walter Hamor Piston Jr., , was an American composer of classical music, music theorist and professor of music at Harvard University whose students included Leroy Anderson, Leonard Bernstein, and Elliott Carter....

 (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

Root (chord)

In music theory, the root of a chord is the note or pitch upon which a triadic chord is built. For example, the root of the major triad C-E-G is C....

 changes as they occur, reveals important and distinctive features affecting the style

Music genre

A music genre is a categorical and typological construct that identifies musical sounds as belonging to a particular category and type of music that can be distinguished from other types of music...

 and texture

Texture (music)

In music, texture is the way the melodic, rhythmic, and harmonic materials are combined in a composition , thus determining the overall quality of sound of a piece...

."

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

Baroque music

Baroque music describes a style of Western Classical music approximately extending from 1600 to 1760. This era follows the Renaissance and was followed in turn by the Classical era...

 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

Alexander Scriabin

Alexander Nikolayevich Scriabin was a Russian composer and pianist who initially developed a lyrical and idiosyncratic tonal language inspired by the music of Frédéric Chopin. Quite independent of the innovations of Arnold Schoenberg, Scriabin developed an increasingly atonal musical system,...

's music features an increasingly slow harmonic rhythm beginning in his middle period.

Prelude no. 1 in C major  (BWV 846) from J. S. Bach

Johann Sebastian Bach

Johann Sebastian Bach was a German composer, organist, harpsichordist, violist, and violinist whose sacred and secular works for choir, orchestra, and solo instruments drew together the strands of the Baroque period and brought it to its ultimate maturity...

s Well-Tempered Clavier illustrates the difference between melodic and harmonic rhythm: through a constant stream of sixteenth note

Sixteenth note

thumb|right|Figure 1. A sixteenth note with stem facing up, a sixteenth note with stem facing down, and a sixteenth rest.thumb|right|Figure 2. Four sixteenth notes beamed together....

s, Bach changes chords

Chord (music)

A chord in music is any harmonic set of two–three or more notes that is heard as if sounding simultaneously. These need not actually be played together: arpeggios and broken chords may for many practical and theoretical purposes be understood as chords...

only once per measure.

Source

• Piston, Walter (1944). Cited in Swain, Joseph P. (2002). Harmonic Rhythm: Analysis and Interpretation. ISBN 0-19-515087-2.