What Are Aleatoric Elements in Music?

Chance music allows the composer to roll the dice with compositional elements.

Although the first half of the 20th century saw an increase in highly formalized and restricted compositions, the second half saw the emergence of a restrictive antithesis. Composers were starting to write music that gave the performer more control over the performance of a piece of music. Aleatoric music gave additional creative responsibility to the performer and left some elements of the music up to chance. Keep reading to find out more about this extraordinary development in Western art music.

Aleatoric Music

Aleatoric music gives more creative responsibility to the composer.

Aleatoric music allows the performer to control certain aspects of a composition. The composer will decide ahead of time which elements are aleatoric. The elements left to chance can include one or all of the following elements: medium, expression, duration, pitch or form.


Instruments may be left to the performer to decide in chance music.

The medium is another way of talking about the instruments employed in the piece. Much like the beginning of the Baroque period where pieces didn’t specify particular instrumentation, in the 20th century, some pieces allowed for performance on a variety of instruments. The main requirement would be whether the instrument could perform the music. If the instrument was suited to the part, then it was acceptable to use it. This allowed performers greater variety in the overall ensemble sound and texture.


The dynamics of the piece may be left to the performer with aleatoric music.

Expression is not the expression that one might carry on his face when trying to play a difficult passage. Rather, it is the dynamics, or loudness and softness, of a piece. By allowing the performer to choose how loud or soft to play certain sections, a freedom in interpretation arises. The performer can choose to play a piece quietly to create a somber mood or loudly to inspire emotion or even fear. The dynamic level of a piece can drastically change the perception of the work.


How long to hold specific elements may be left to chance.

Duration refers to the individual pitches length and could refer to the actual time that a section repeats. Musicians may play a particular motive for an unspecified length of time. They may also have to choose how fast or slow to play the piece. Duration can drastically alter the sound of a composition. Try playing Brahms at a snail's pace and it will begin to sound a little like Wagner.


The highness or lowness of pitch can be determined by the performer.

A composer might choose to allow the performer to pick from a set of several pitches or may write a rhythm in which the performer must decide upon the pitches. This type of modification can have a drastic effect on the composition. With performers given the freedom to change pitches, no two versions of the piece will be alike. It is possible to listen to the same piece several times and not be able to identify it by anything but the rhythm.


The formal building blocks can be moved around in chance music.

The form is the final element that composers of aleatoric music will leave up to the performer. With this type of change to the piece, the performer might be able to move entire sections. The middle of the piece might become the beginning and the beginning may move to the end. The piece can be reordered and played in such a way that it doesn't ever have a true ending. This can be useful for performers who need a piece of a set duration. By choosing the form, the composer has assured that every section is complete in itself. This allows for any combination of "musical blocks" to be set together.


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