Generative Creativity - lecture 9;
Soundscapes and sonification
Introduction
While generative methods are often used to produce note-based
music, they are also used to produce more general forms of sonic
experience, i.e,. `soundscapes'.
This can take the form of
sonification
algorithmically-mediated sonification
simulation-mediated sonification
Brian Eno on generative music
Key figure for ambient/generative music and creator of the seminal
`Generative Music 1' album from 1996.
Views generative music as `the blending of several independent
musical tracks, of varying sounds, length, and in some cases,
silence. When each individual track concludes, it starts again
mixing with the other tracks allowing the listener to hear an
almost infinite combination'
Mapping from text to soundscapes using low-level parameters (e.g.,
words and phrases) and higher-level constructs (e.g., plot
developments) and including some of the original text.
Work by Daniel Cummerow from 1998 involves algorithm-mediated
sonification of mathematical constructs, e.g., the prime numbers.
Begins by converting the sequence into base 3 notation.
The first 10 primes are then 2 10 12 21 102 111 122 201 212 1002.
Generation of bass part
The 3rd digits of the first 941 prime 9 (zero-padded) numbers were
used.
The note values were determined by the number of consecutive
prime numbers with the same 3rd digits.
This value defines both the number of tied sixteenth notes and number of
scale steps relative to the previous tone.
0 is a pause, 1 means descend and 2 means ascend.
The initial pitch is F so the first tone is G#.
Generation of treble part
This was determined by the unit digits of the prime
numbers.
For the 1st - 428th prime numbers the tones are determined the
same way as the 1st part. It then pauses while the 3rd part
executes.
When the 3rd part is done, the 2nd part does the same using
the 569th - 1002nd prime numbers in the following way:
Start at F, 1 means descend a scale step, 2 means ascend a
scale step (there are no zeros). When done, double the 3rd
part to the end.
Combination procedure
For the 1st - 428th prime numbers, this part doubles the 2nd.
Then between the 429th - 463rd prime numbers, it uses the
whole prime numbers (they have 8 digits in this interval)
concatenated.
Starting at F, 0 and 2 means ascend a scale step, 1 means
descend a scale step.
When it's done, it hooks up at the prime number where the 1st
part is at the monent and uses the same algorithm as the 2nd
part had at the beginning of the piece.
When the 2nd part is done, the pitch jumps back to the default
F, and then continues as before to the end.
Cummerow has tried to map tones out of a
mathematical structure. But why?
The assumption must be that the quality of a piece of music depends
on its structural properties.
So find something non-musical with interesting structural
properties and map it into music and you should get interesting
music?
Fractal music
Fractal music follows the same general approach as Cummerow's
maths-based compositions.
But in this case, the mathematical structure is a fractal,
a generatively specified object which is
infinitely detailed.
This means you can `zoom in forever'.
These objects are useful for graphics and image applications
(they're a great way to generate images of trees) and feature
extensively in the area of algorithmic art.
Generating music from fractal objects
For generation of musical output from fractals, data from the
fractal construct are converted to musical parameters to create
melodies, harmonies, rhythms, textures, etc.
This is most easily done by representing the factal in some sort of
visual form. Then, we might...
Draw a line across the image and map the RGB values into
tones/durations.
follow the orbit of an attractor (if there is one) for
successive iterations and map the values of coordinates along
that path to a pitch.
As usual there is the problem that while fractals clearly have
interesting structural properties, these may not translate easily
into interesting musical structures.
Using the Notes applet as a base, create an applet that plays
scales in C, starting from middle C (midi code 64). The applet should
repeat the scale 10 times.
Modify the applet so that it plays the scale until the page is
exited. This will involve running the main loop in a thread which is
then terminated when the browser calls the applet's 'stop' method.
(Check the JApplet documentation for details.)
Modify the applet so that it plays the ascii codes from your
first name (treating them as midi values) over the top of the
scale.
In the Fibonacci sequence, each number is the sum of the
previous two (using zero at the start). Modify the applet so that
it plays all the midi codes in the Fibonacci sequence up to 127
over the top of the scale.
