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Predictability, Surprise, and Randomness in music.

Satisfying music balances predictability and surprise.  Our minds are trained to know what event comes next in music. If you listen to 100 folk songs, the sequences of chords and rhythm all have a logic that sounds good to the ear.  When someone writes a new song, they’re essentially starting with a chord and then using their ‘music recognizer’ to suggest what comes next.

But music that is entirely predictable is trite and boring. You want to hear something unexpected from time to time. The genius of Western classical harmony is that when you drop in a note that’s unexpected, possibly dissonant, there are available harmonic resolutions that ‘add up.’  So you get a surprise but it’s followed with something that’s expected.

There’s another dimension besides Predictability & Surprise: Randomness.  Random sources are a fundamental component in modular synthesis.  You can connect a noise source to a sample & hold module, and it will pick out random values every time you trigger it.  It frees you from having to think the notes up yourself. It’s an endless source of novelty.

The problem with purely random sequences of notes or rhythms is that they can sound arbitrary and devoid of authorial intention.  A good composer will make music that is imbued unmistakably with their personality. Random sequences do not have that intentionality and personality.

Random input into music is not entirely useless.  If you start out with something predictable: a 2 bar loop that repeats, you can add some precise with, for example, randomly modulating the filter cutoff. You hear the same notes in the same rhythm but the timbre changes continuously.

Never doing anything by half, I often patch in many random modulations into a patch.  For example I’ll take a sound sample and slice it to pieces, then chose slices at random to play back.  Then process the signal with a bandpass filter that’s also randomly modulated.  But the trigger driving the sampler – selecting each new slice and filter cutoff – will come from a regular clock.  So there’s some rhythmic predictability that interacts with the constant surprise.

It helps me make the music I want to make.  The random inputs into the music seem to rhyme with the way randomness affects my life constantly.  Paradoxically, when you steadily inject randomness into your music, it has it’s own predictability.  The ear expects the randomness, and it inverts the role of surprise in the music. It’s surprising when the random process produces something that the ear might expect, based on our inborn and learned intuitive knowledge of music.

There’s another layer to how randomness works in music: the human mind and senses are adapted to finding patterns in chaotic input.  This is valuable for survival. If your eye can catch the twitch a black tail in a tree tossed by the wind in low light, you can avoid being attacked by a panther.  But when presented with truly (or mostly*) random input, your mind will find pattern in it.

This all means – to me at least – that randomness isn’t inimical to musical expression, but can add to it.   When one adds randomness the process of tuning it’s effects adds an intentionality to it’s action on the music.  Maybe in how a composer tunes the randomness can be a conduit for the composers personality as much as their choice of notes and rhythms.

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