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What is Aleatoric Music?

Aleatoric music is a form of music subject to improvisation or structured randomness. It is a type of music performed using some form of probability. Many composers were intrigued by Aleatoric music where the melody and rhythmic flow were left up to chance using the dice.

Therefore aleatoric music is subject to chance, pretty much like the atoms in quantum physics. It involves playing instructions from sheet music written by the composer, and improvisation by the musician playing the piece.

History of Chance Music

Aleatoric music is also known as chance music. In the Renaissance and Baroque periods, composers wrote with figured bass notation, leaving a degree of performance choices to the composer. During the Classical music era, Mozart invented a musical dice game called Musikalisches Würfelspiel that applied the use of chance to the content of specific musical measures.

Despite composers experimenting with chance music, it only came forth in the 20th century. Classical music composers like Charles Ives, Henry Cowell, and Alan Hovhaness included small sections in pieces where performers could improvise. John Cage fully embraced aleatoric music in 1951 and debuted the “Music of Changes” - it demonstrated how the same piece of music could be played in different ways depending on the performer’s choices.

Creating Aleatoric Music

A songwriter of aleatoric music can create a melody line for their chorus or refrain randomly by creating a dice. The composer would then follow up with logical chord progression and rhythmic flow that would like the music phrase more cohesive.

Jarbas Agnelli’s “Birds on a wire” used the position probability of real birds sitting on five real wires that reminded him of music staff for his chance composition.

How is Aleatoric Music different from Atonal Music?

Atonal music sounds random like aleatoric music. So, what sets them apart? Atonal music is actually more random compared to chance music. It can sound a lot like aleatoric music, but it does not follow the traditional concept of a key or a mode.

Aleatoric music offers the probability to take the wheel in the composition. On the other hand, atonal music is carefully and purposefully created one note at a time. Those notes don’t follow the rules that our ears are used to hearing in Western music styles.

Aleatoric Music in Film Scoring

You might be surprised to know that Aleatoric music has been used in film scoring. John Williams’s partially aleatoric score for Robert Altman’s film “Images” earned him an Academy Award nomination. Mark Snow occasionally turned to aleatoric music in the long-running sci-fi TV series “X-Files”. Radiohead guitarist and avant-garde composer Johnny Greenwood has also used aleatoric techniques in the scores for Paul Thomas Anderson movies.

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