Aleatoric Music

Cover Art: Sophie Cheng

Aleatoric music is the result of incorporating an element of chance into the process of creating music. There are many ways composers have developed to accomplish this; different aleatoric techniques involve random sources used to compose the score, in the performance of the music, and randomness inherent to the instruments themselves. All of these methods have their own names and subdivisions, but by employing a technique known as laziness, this article will use ‘aleatoric’ as an umbrella term to describe all of them. When taken to the extreme, aleatoricism can break down the boundaries that we would normally use to define music, and that’s what this article is going to be about. Get excited.

Aleatoric Composition

The oldest type of aleatoric music involves deriving a melody from an independent source over which the composer has no control. During the 18th and 19th centuries, classical and romantic composers would roll dice to generate notes, adding duration and accidentals after the fact to create a melody. Wolfgang “The Wolf”' Mozart actually developed his own dice game for writing waltzes. The numbers you roll give you a number on this board, a number that corresponds with a small snippet of music. By patching these snippets together, you can create over 45 quadrillion different waltzes.

For our etymology fans, these games are likely why the word “aleatoric” is associated with music at all, given that it comes from the Latin aleator, which means “dice player”.

A more modern instance of using an independent external source for music is Jarbas Agnelli’s 2009 piece, “The Birds on the Wires”. Agnelli took a picture of pigeons sitting on telephone wires, treated the wires as a 5-line staff, and converted the birds into notes, creating a melody, as shown in this animation.

Converting an external source into music is considered by scholars to be the lamest form of aleatoric music: once you write a piece of music this way, it is going to stay the same every time it’s performed, and that’s small potatoes. In the mid-20th century, a golden age for experimental music, composers developed techniques of aleatoric sound which yielded pieces that could never be played the same way twice.

Aleatoric Performance / Player Choice

The most common aleatoric technique involves giving the performers some agency in how the music will sound. Unlike “The Birds on the Wires” or Mozart’s musical game of Yahtzee, which only deal with composition, the randomness here comes in during the actual performance of the piece, so that the music is generated not only by the composer, or in fact by any individual, but instead emerges from the choices of the people who play the instruments.

Looking through examples, we can see that the more creative power is disseminated to the player from the composer, the more the music can vary from performance to performance.

Early versions of this technique were pioneered by a few classical composers trying to create chaotic and detailed sounds without overly complicated tempo markings. Composers like Alan Hovanhess, Witold Lutoslawski, and Krzysztof Penderecki would write phrases between two repeat bars, along with the words “Ad Lib,” indicating that the player should play the phrase repeatedly and that they could determine certain characteristics about the performance, like the meter, volume, or emphasis. By surrendering some of the creative power to the players, the composers were successfully able to achieve effects like this moment in Hovhannes’s “Magnificat.”

Penderecki’s 1961 “Threnody for the Victims of Hiroshima” puts player choice into great effect. By using the same looping mechanism as Hovhannes, leaving some parts of the written music up to interpretation, and even allowing players to determine the order of notes at times, Penderceki was able to create a certain chaotic texture that works really well given what the piece is trying to emulate.

The Beatles have used this type of aleatoric sound in their 1967 song “A Day in the Life” . In a transition in the middle of the song, all the musicians in the orchestra move from the bottom of their instrument’s pitch to the very top, with no restrictions other than that they had to reach the final note at the same time.

Some composers wrote pieces that are entirely based around the choices of individual musicians - rather than having performer determination as a device for just a single passage. As a result, while the previous three examples will mostly sound the same except for a few moments of slight unpredictability, these pieces can sound entirely different depending on the performers.

For example, John Cage’s “ASLSP,” a piece with the unconventional tempo marking “As Slow As Possible,” sounds similar each time it is played, except for its length, which is determined by how long the player is willing to hold out. Most play for about an hour, but one live performance has lasted for a whole day. A specially designed organ in Halberstadt Germany started playing the piece in 2001 and is scheduled to end in the year 2640!

Terry Riley’s “In C”consists of an unspecified number of performers, playing unspecified instruments, moving through 53 simple musical phrases (all in the key of C), repeating them an unspecified number of times. Each ensemble of players can choose its own instrumentation and tempo for the piece, and individual players choose how many times they play each phrase. The result is a chaotic performance lasting an indefinite amount of time and whose instruments drift in and out of sync unpredictably.

A piece with a similar gimmick as “In C” is “25 Pages” by Earle Brown. The pages of the piece are unnumbered and must be rearranged by the performer. The pages can even be turned upside down. What’s more, the player decides the tempo as well as the clef, meaning variations can sound wildly different from each other.

The most extreme example of giving creative power to performers must be “Treatise” by Cornelius Cardew. The score of “Treatise” looks less like written music and more like written music that’s been put in a blender, or an MC Escher painting (this guy), or something out of the movie Arrival. A score so open to interpretation breaks down the barrier between composer and performer almost entirely. So many of the decisions are made by the performer that the score of “Treatise” may not qualify as music. A pretty strong argument can be made that everyone who performs a rendition of “Treatise” composes their own piece of music, and it just so happens that they were all inspired by the same piece of visual art. Alternatively, maybe what makes “Treatise” music is the fact that it was written with the purpose of being read as music.

Indeterminacy in Instruments

John Cage’s “Imaginary Landscape No. 4” has an unchanging score, extensive instructions for the performers to follow, and predetermined tempo, instrumentation, and ensemble size. Despite these shared characteristics, no two performances are alike, because “Imaginary Landscape no.4” is played using twelve radios. Two players operate each radio according to the score’s instructions, the first controlling the volume and timbre of the radio’s sound and the second controlling the frequency that the radio picks up. The sound is the public broadcasts picked up by the radios: a sea of static, with the occasional snippet of music or speech. John Cage couldn’t predict what any rendition of “Imaginary Landscape No. 4” would sound like, and neither can the people who play it, nor do they have any choice in the matter; the instrument is given the sole creative power of the piece.

If the material of music is generated by the instrument alone, is it possible to have music entirely without a composer or performer? The answer, as all answers do, lies in Zadar, Croatia. Zadar, Croatia is home to the world’s largest and only sea organ, a structure that uses the ocean waves to produce music. The waves push air through underwater pipes, which flows out through holes above the water and creates various tones. A lot of the writing you’ll find about the sea organ talks about the ocean as if it were a musician playing the organ, but it’s probably more accurate to describe the organ as a massive instrument, with the ocean being just one component. The aleatoric music of the sea organ is created without a composer or a musician.

Video games!

It’s not uncommon for a games’ soundtracks to change according to the player’s actions, making video game music an interesting and very unique branch of aleatoric music. The element of chance in video game music comes not from a composer or performer, but entirely from the audience.

Let’s take as an example, Way to Go, a simple interactive game with a player-responsive soundtrack. The music changes tempo depending on whether the player is walking or running, and adds sounds when the player jumps or flies. The music that results from any run of Way to Go, or games like it, can be viewed in two ways: as randomness in composition or randomness in instruments. Like “Treatise” or “25 Pages,” the choices of the performer, the player of the game, ensure that the soundtrack will never be the same twice. However, from the perspective of the player, who knows how their actions will affect the music, the only source of randomness is their instrument, the game, whose soundtrack progresses independently of their actions.

Adding an element of randomness into the creative process is a really interesting phenomenon because to some extent it removes the element of intent. Most definitions of music, and art generally, require that a work have intent behind it; the intent to evoke emotion, to convey a message, or to reflect the world in some way. However, some of the music we’ve looked at, think “Treatise” and the sea organ, has no intent at all; these don’t reflect a message by a composer in any form. In a way, aleatoric music gives that power to the listeners, who become free to interpret and assign meaning to the music without sparing a thought to how the artist may have intended it.