Generative MusicBy: Ryan Bone, Andrew Reed, Kevin Ekeberg, Hector Medina-Fetterman, Chase Plante

What is Generative Music?● Constantly changing● Created by a system

Types of Generative Music● Structural● Behavioral● Creative● Emergent

History● 3000-1100 BC

o Wind chimes

History● 15th Century

o Multi-mode pieces Missa cuiusvis toni (Mass in any mode),

Johannes Ockeghem

History● 18th Century

o Musikalisches Würfelspiel (musical dice game) scripthica.com

History● 20th Century

o Algorithmic Generation Stochastic Grammar-based Evolutionary Learning systems Hybrid systems

Grammars● Grammars have been used in

music theory and analysis since the 1980s

● By converting grammatical strings to sounds, pitch, and durations, music can be formed

L-Systems● A type of rewriting system and

formal grammar● Developed in 1968 by a dutch

biologist● They can be used for many

applications, ranging from generating fractals and trees, to music and terrain

L-SystemsThe Grammar can be represented as the following tuple

G = (V, α, R)

where

● V is the alphabet, or the set of symbols in the grammar

● α is the axiom, or initial state of the system. This a string made of symbols from V.

● R is a set of replacement rules that replace one symbol string with another.

o For example. A → BCD would tell you to replace the symbol A with BCD when you encounter it

o If a character does not have a rule we don’t do anything with the symbol

L-SystemsL-Systems are processed from left to right.

Given the rules:

R1: A → BCD

R2: B → E

R3: C → A

and the Axiom “A” we can get the following

strings over 5 iterations

Iteration String

1 A

2 BCD

3 EAD

4 EBCDD

5 EEADD

L-Systems● Using this deterministic context-free

grammar, we would not be able to

generate randomness.

● We can add randomness by assigning

more than one rule to a symbol, and

then giving the rule a probability of

occurring. This is called a stochastic

grammar

● Using this framework, unique yet

“similar” strings can be formed.

L-Systems

● We’ve generated strings, but now need

to turn it into music

● By assigning a sound to each symbol,

music can be generated

● Complexity can be added by adding

symbols that denote duration and pitch

Generative Grammar Examples

● http://www.pawfal.org/dave/blog/2008/12/l-system-music-revisited/

Generative Music Software● SSEYO Koan Pro (1994 - 2007)● Intermorphic

o Noatikl (2007 - present) Replaced Koan

o Mixtikl (2004 - present) Portable solution

● Unityo G-Audio Editor Extension

Generative Music Software

Games with Generative Music

● Emergent - Beat Buddy by Threaks● Behavioral - January by Disasterpeace

Xenochrony ExampleFrank ZappaRubber ShirtSheik Yerbouti1979

Xenochrony

“Strange synchronicity”

A product of confirmation bias

Xenochrony in GamesAmbient exploration musicRhythm heavy combat musicExample

Vertical LayeringDefinition of layering- “Recording (or playing) a musical part with other several similar sound patches playing simultaneously to add more body or fullness to the recording.”

Definition of vertical - “indicates a simultaneous event such as the sounding of several concurrent notes in a chord”

In other words, the technique of vertical layering is to use distinct tracks or parts and play/stop them at different intervals on top of one another to create different moods depending on a variety of variables (Ex: start/end of combat, scripted moment).

Vertical LayeringVertical Layering is used due to its versatility & adaptive nature with generated music. Depending on the number of tracks you use, you can create the same song but with different emotional hooks depending on which track the listener hears first.

Demo:

Vertical LayeringThere are two different techniques for Vertical Layering:

Additive- All of the tracks are designed to be played together at once or with a select group of other tracks. The music will still sound good if certain tracks are or are not playing.

Interchange- Some of the tracks are designed to be swapped with other tracks. Adding layers freely is not the goal here, but it is possible should the composer allow it.

Horizontal ResequencingDefinition - the method by which pre-composed segments of music can be re-shuffled according to a player’s choice of where they go in a storyline or environment.

Horizontal refers to the passage of timeResequencing is the reordering of tracks

This uses tracks that “interrupt” one another in order to convey something to the player, such as how much time is left on a button press/power-up. The “interrupt” track is designed to mix in and out with a main track (or be a part of the main track) depending on the current state of gameplay.

Horizontal Resequencing & Vertical Layering Game Example

Game: Super Mario Galaxy 2

Level:“Saddle Up With Yoshi”

Composer:Koji Kondo & others

ReferencesGrammar Based Music Composition http://www.csse.monash.edu.au/~jonmc/research/Papers/L-systemsMusic.pdf

Temporality, Intentionality, and Authenticity in Frank Zappa’s Xenochronous Works http://researchblog.andremount.net/?p=476#2f

Modeling Plants with Lindenmayer Systems http://www.allenpike.com/modeling-plants-with-l-systems/

3d Lindenmayer Systems http://www.geocities.ws/gplatl/LSystem/LSystem.html

A Composer’s Guide to Game Music http://winifredphillips.wordpress.com/2014/03/06/a-composers-guide-to-game-music-vertical-layering-part-1/

Music Dictionary http://www.music-dictionary.org/Layering

Questions?