MUS 312 Form & Analysis

N. The Roles of Chance and Choice in 20th-Century Music

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There has been a general tendency in Western music to restrict the performer's options ever more closely, and at the same time an increasing dedication to honoring the composer's intentions at the expense of the performer's creativity.  However, an important force in music in the second half of the 20th century has moved in just the opposite direction, toward less control by the composer and more creative responsibility for the performer.  This new responsibility can range from making an insignificant decision to shaping all aspects of a piece.  In either case, the composer deliberately leaves something unspecified, up to chance or to the whim of the performer.  Two terms for music of this sort are indeterminacy and aleatory, which mean essentially the same thing.

These two approaches--chance in composition and choice in performance--form the two related branches of experimental music, a term that is appropriate for any music in which the final product is deliberately kept beyond the control of the composer.

Chance in Composition

In order to allow chance to play a part in composition, the composer must decide what aspects of the work are to be decided by chance and what the range of probabilities of each aspect should be.

The most influential composer to make extensive use of chance in composition is American composer John Cage.

Only the imagination limits the variety of means which may be used by a composer to determine the element of chance:  I-Ching (Chinese treatise on probabilities), imperfections in paper, even machine gun fire aimed at manuscript paper!

Computers have been used to some extent in this regard, since they can be programmed to produce an apparently random series of numbers within a specified range and to use those number in decision-making processes.  Using a computer, the probabilities can sometimes be quite complex.

A very simply example may be as follows:

Suppose we want to generate a melody that will conform to the following rules:

  • Use only the notes C, E and G.
  • Allow no repeated notes.
  • Use fewer G's than C's or E's.
  • Distribute the C's and E's evenly.

The following table would tend to produce such a melody, although we still must specify its length and the first note.  (For instance, if C is the most recent note generated, then the next note will probably be E [75%], but might be G [25%].)

  C E G
G 50% 50% 0%
E 75% 0% 25%
C 0% 75% 25%

Conditional probabilities can be nested to any depth, with the result that the selection of a particular event may depend upon the result of the last several decisions.

Lejaren Hiller is a composer whose name is often associated with computer composition.  Together with Leonard Isaacson, he composed the first serious computer piece, the Illiac Suite for String Quartet, in 1957.  Other composers associated with computer probability composition include: Iannis Xenakis, Larry Austin (a USF prof!), Barry Vercoe.

Choice in Performance

Aleatory in performance can range all the way from the most insignificant detail to the entire shape of a piece.  In the latter case, the result may be an entirely different sound each time the piece is performed.

The elements of composition that may be left up to the performer include the following:

  • Medium (instrumentation)
  • Expression (dynamics, etc.)
  • Duration (rhythm & tempo)
  • Pitch
  • Form

Composers interested in allowing the performer to have more freedom frequently omit expression marks, etc.

Some composers wish to exercise only a limited amount of control by leaving durations up to the performer.  In such cases, proportional notation is used, where the spacing of the notes on the page indicates their approximate durations.

A simple example of pitch indeterminacy is the instruction "as high as possible."  More extended examples often show the general contour of a desired line.

The usual method of leaving the form of a work unspecified, short of total improvisation, is to allow the performer or conductor to choose the order in which sections of a piece will be performed, or whether they will be performed at all!  This approach to form is sometimes called open form or mobile form.

Some composers associated with pieces which utilize performer indeterminacy are:  Stockhausen, Morton Feldman, Lukas Foss, Cornelius Cardew, Witold Lutoslawski.

Graphic Scores & Text Scores

A graphic score is one in which conventional musical notation has been abandoned in favor of geometric shapes and designs that suggest more or less how the music is to be performed.  Some composers associated with graphic scoring are:  Feldman, Martin Bartlett, Robin Mortimore.

A text score is one that consists only of words.  The text usually provides instructions for an improvisation, but it may do little more than set a mood.  Some composers associated with text scores are:  Stockhausen, Christian Wolff, Dick Higgins.

Music on the Fringe

In the 1960s and 1970s especially, a number of composers wrote pieces that seem to many musicians to push the limits of what can be called "music."  Traditional definitions of music often include references to organized sound and to the expression of ideas and emotions, but some works challenge these notions.

Some composers associated with "fringe music" are:

Dick Higgins:  includes works where persons simply listen to environmental sounds.

Pauline Oliveros:  environmental theater piece that uses an entire city or university as its performing stage.

Mortimore:  one piece contained the instructions:  "Play until 2000 A.D."

Paul Ignace:  retitles works, such as a "Symphony No. 2," which is a repeat of Symphony No. 1, heard the previous night.

David Cope:  "danger music," which suggests self-directed violence.

Takehisa Kosugi:  instructions include: "scoop out one of your eyes five years from now."

Philip Corner:  "One Antipersonnel-Type CBU Bomb Will Be Thrown into the Audience."


Experimental music, in which the composer consciously abdicates control over the compositional process or the performance, or both, has been an important element of music in the second half of the 20th century.  Chance in composition has involved the use of a number of decision-making techniques, including the I-Ching, while the computer has made practicable aleatoric compositions that are much more complex.  The element of chance--or, from the performer's viewpoint, choice--has been even more influential in the performance of music than in composition.  The improvised portions of a score may be insignificant, or improvisation may be the major element of interest in the work.  New notations have been devised for indeterminate music, including proportional and graphic notation; text scores dispense with notation entirely.  Finally, a number of "fringe" movements have ranged from the absurd to the violent, calling into question our notion of what music really is.

Minimalism & Neoromanticism

Minimalism and neoromanticism are two important trends in more recent music.  They both developed first in the United States and only later were adopted by European composers.

Minimal music, also called process music, phase music, pulse music, systemic music, and repetitive music, may have had its roots in some of the works that Cage, Wolff, and Feldman composed in the 1950s, but the first important example of what has become known as minimalism was Terry Riley's In C (1964).

Some of the characteristics of minimalist music include:

  • Restricted pitch and rhythm materials
  • Tonal (or neotonal) language
  • Diatonicism
  • Use of repetition
  • Phasing (moving out of sync)
  • Drones of ostinatos
  • Steady pulse
  • Static harmony
  • Indeterminacy
  • Long duration

Many of these aspects are also found in some kinds of Eastern music, as is the meditative quality characteristic of many minimalist works.  Riley, Steve Reich, and Philip Glass, the three Americans most closely associated with minimalism, all studied Eastern music.  Glass' study of the improvisations of Ravi Shankar was especially important in the development of his mature style.

Neoromanticism is the term used for "romantic-style" music usually superimposed on an atonal, avant-garde background, or swallowed up in a collage of other quotations in a "stream-of-consciousness style."

George Rochberg is a composer whose name is perhaps most closely associated with this style, although there are many others:  David Del Tredici, Krzysztof Penderecki, Frederic Rzewski, Ladislav Kupovic.


While the post-serial avant-garde tradition has not died out, it has certainly met with serious opposition in the forms of indeterminacy, minimalism, and neoromanticism.  Indeterminacy was a reaction against the total control that is the basis for serialism.  Minimalism opposes the atonal ideas of the incessant recycling of pitch material, of constant variation, and, of course, of atonality itself.  Neoromanticism does these things, too, but it represents also a complicated relationship between today's composers (and listeners) and the music of the past.

And so 20th-century music continues as it has always been--a maddening but fascinating collage of approaches and materials, a period without a style.

Popular Music Form

Chorus (refrain)

These are the primary sections found in many pop songs.  Naturally, there are typically repetitions of verses and choruses.  The bridge is a modulating section.

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