What Is Aleatoric Music? With 7 Top Examples & History

Heard the term aleatoric music but have no knowledge on the subject? In this article we explore what aleatoric music is, the history, and give video examples. So read on.

What Is Aleatoric Music? Definition

Aleatoric music, which incorporates randomness, is an experimental style popularized in the 1950s and 1960s. It is technically classical music, though it doesn’t sound much like it.

The genre relies on chance and planned randomness, and uses features like indeterminate rhythms to create fascinating music. Said in different words, the primary way aleatoric music differs from traditional classical music is that part of the composition is left to the performer.

While Mozart and Beethoven wrote notes on a page for the instrumentalist to follow, aleatoric composers instead give generalized instructions and leave it up to the performer to make decisions. These can affect just about any element, according to the composer’s wishes:

• Pitch
• Harmony/alternative lines
• Rhythm
• Register
• Timing/duration of the piece
• Articulation
• Dynamics/musicality
• Number of instruments or notes played at once
• Number of performers
• Location of hands on the instrument
• Expressive elements like vibrato or rubato

Aleatoric Music Characteristics

Most, but not all, aleatoric compositions use sheet music for the performer to follow just as in any other type of written music. However, some rely on shapes or other markings rather than traditional notation, with a graphic score commonly used to read a piece.

Aleatoric music is highly-creative, with the composer and performer working together to present a piece of music that sounds different every time. It’s spontaneous, imaginative, and unpredictable, giving the performer lots of choice.

As a result, the audience doesn’t know exactly what to expect, unlike pieces from the Classical era (for example) that follow a controlled structure, such as rondo or sonata. 

Some performances use unpredictable rhythm, making a sound scattered and unfocused, like dropping marbles onto the floor. Other pieces also use pitch randomness, meaning it’s impossible to sing along without a grounded tonal foundation.

An aleatoric composition is fundamentally right-brained, using systematic and mathematical functions to decide how the music should go. The abstract sound of many aleatoric pieces means it isn’t always accessible to those without musical training.

7 Examples of Aleatoric Music

These seven examples of music are varied but illustrative of the aleatoric genre.

1. “Music of Changes”

One of the quintessential pieces of the aleatoric subgenre, “Music of Changes” incorporates the I Ching, an ancient Chinese text, to provide its randomness.

John Cage gave this masterful work to the world in 1951, when aleatoric music was still unfamiliar to most classical musicians. It remains one of the foundational works of aleatory, and influenced many later works from other composers.

2. “First Symphony”

Alfred Schnittke’s vision for aleatory successfully combines ideas from Western classical tradition with contemporary chance.

This large and loud symphony contains everything from a Baroque rondo to jazz improvisation. It even requires choreography from the musicians as they enter and exit the stage at various points during the four-movement piece.

3. “Klavierstuck XI”

Composed by Karlheinz Stockhausen in 1956, this work uses musical fragments, leaving it up to the performer to decide in which order to play them.

They may plan the structure ahead of time and practice it accordingly, or let it be a spontaneous onstage decision. This piece for solo piano is a favorite of touring virtuosos.

4. “Threnody to the Victims of Hiroshima”

This classic work of aleatory is intense and eerie. The composition allows 52 string players to decide on performance timing and techniques, including percussive slapping and pizzicato noises to represent trauma and terror.

Krzysztof Penderecki wrote the piece in 1961 as a memorial to Japanese civilians killed by the atomic bomb that helped end World War II. “Threnody” brought about a Neo-Romantic style and won a UNESCO prize for its cultural impact.

5. “Intersection 2”

Morton Feldman’s work for solo piano, which dates from 1951, is a perfect example of chance music that sounds random but realistically involves quite a bit of planning.

“Intersection 2” explores the sounds of aleatory by letting the performer decide multiple elements of the piece, such as pitch and rhythmic organization.

The graphic score for this piece is famously made up of intersection squares and lines, representing a road map for the pianist to follow onstage.

6. “In C”

Terry Riley wrote this piece in 1998, and it quickly rose to the top of the chance music canon. This score displays fragments of musical bars in the key of C, then allows the performers to decide who plays which one in which order.

The mastery of this work lies in its contrast of aleatory with minimalism.

7. “Nebula”

Another example of an aleatoric graphic score, “Nebula” involves materials like dirt and spray paint to visually represent the sounds for the performer to interpret.

American composer Brian Scorn is a visual and graphic artist who sometimes crosses over into the world of music. He tours and presents his imaginative art in galleries and music venues all over the world.

Top 5 Aleatoric Musicians

One key way to understand the question “what is aleatoric music?” is to learn about the musicians connected with it. No one country is a focal point for the genre’s development; the composers come from all over the world.

1. John Cage 

Cage is well known as one of the top creative thinkers and experimenters in modern classical music. His biggest claim to fame, “4’33” (“Four Minutes and Thirty-Three Seconds”), features a pianist sitting silently at the bench to let ambient noise create the musical piece.

Emerging from an eccentric and imaginative mind, Cage’s work with aleatoric music was extensive, making him one of its most significant pioneers.

2. Pierre Boulez

A French composer, performer, and conductor, Boulez was an influential figure in the development of aleatory music. His primary contribution was the naming of it.

Taken from the Latin for “dice” or “chance,” he used the word alea to describe the randomness in indeterminate compositions. Boulez also composed some aleatoric music himself, though it was more controlled than later composers.

3. Witold Lutoslawski

Heavily inspired by Cage in the 1960s, Lutoslawski accepted the basic concepts of aleatoric music but traveled in a unique direction with them. Rather than leaving entire pieces to chance, he, instead, wrote sections of music that incorporated indeterminacy. The result was less random than earlier forms of the style.

Much of Lutoslawski’s music symbolizes the political upheaval of his native Poland in its mid-20th Century struggle for freedom from the Soviet Union.

4. Gyorgy Ligeti

First living in communist Hungary, Ligeti couldn’t fully realize his compositional freedom until he emigrated to Germany in the 1950s.

His most influential works were for film soundtracks, though he wrote for symphony orchestras and avant-garde solo artists as well. His impressive body of work utilizes polyrhythms, atonality, chromaticism, and electronic sounds.

5. Leo Brouwer

The hotbed of aleatory in the mid-20th Century was Eastern Europe, expanding to Western Europe and the United States.

So it’s surprising to see a Cuban composer join the ranks, but that’s exactly what Brouwer did. The composer and guitarist grew up in Havana but received his musical training in the U.S., where he experiments with modern music heavily influenced by the sounds of his native country.

The History of Aleatoric Music

Though aleatoric music is modern, the basic concept of chance goes as far back as the Renaissance. When composers wrote for a vocal or string group with figured bass, that left some choice to the performer. This tradition continued into the Baroque period, inviting string instruments and keyboards to participate.

In the mid-1900s, Charles Ives and a few other forward-thinking composers began to write opportunities for improvisation in their music.

Aleatoric music arrived in the mid-late 20th Century. Often, it incorporates elements of minimalism, 12-tone, electronic, or other forms of modern music (sometimes a combination of more than one).

Besides the composers featured above, other contemporary names have toyed with aleatoric music, such as:

• Gyorgy Ligeti (“Artikulation”)
• Earle Brown (“Available Forms II”)
• Iannis Xenakis (“Pithoprakta”)
• Cornelius Cardew (“Treatise”)
• Alan Hovhaness (“Lousadzak”)
• Tom Phillips (“Golden Flower Piece”)
• Slavek Kwi (“Drawing The Air”)
• Brian Schorn (“Nebula”)
• Pozzi Escot (“Your Kindled Valors Bend”)
• Daniel Schnee (“Chollobhat”)
• John Corigliano (various works)

Sometimes, aleatoric music blends with more traditional styles, and other times it retains its own sound and aesthetic.

What Is Aleatoric Music? Final Thoughts

Like much of modern classical music, aleatoric music is controversial as an art form. Some performers believe it lacks beauty or precision and doesn’t deserve a place in the traditional canon. Others see chance compositions as an interesting experiment that pushes boundaries and challenges listeners to think differently about what they hear.

Whatever your takeaway, aleatory is unique and thought-provoking. We hope you discovered something new from our list!