Chromagram | SuperCollider 3.13.0 Help

Description

A chromagram, measuring the energy at particular chroma within an nTET tuning system.

Possible extension: TODO: Could have arbitrary tuning systems if precalculated the exact fft bin + interpolation data.

Class Methods

.kr

Arguments:

fft	input fft chain, that is, from an FFT UGen
fftsize	FFT size, required for initialisation
n	Equal divisions of an octave, e.g. n=12 is 12TET, 12 steps in an octave
tuningbase	Base frequency or tuning; will correspong to index 0 in results (conventionally, this would be a 'C' in 12TET, but its an arbitrary reference)
octaves	Number of octaves considered from tuning base up
integrationflag	Whether to integrate from frame to frame, off by default
coeff	Coefficient of integration
octaveratio	Default of 2 is a 'normal' octave; other ratios are possible, e.g. Bohlen-Pierce scale uses 13 equal divisions over the ratio of 3 for a 'tritave'
perframenormalize	Defaults to off, but if set to 1 will normalize each frame with respect to itself (as long as there is non-negligible power), potentially providing a more robust measure for comparison between frames (each frame will have then a normalized distribution over chroma, independent of volume)

Examples

(
{

var in, fft, chroma;

//in = SinOsc.ar(440,0,0.1);
in= SoundIn.ar;

fft = FFT(LocalBuf(2048), in);

chroma=Chromagram.kr(fft);

chroma.poll;

Out.ar(0,Pan2.ar(in));
}.play
)

//n TET display

n= 12; //19, 24

(
x = {

var in, fft, chroma;

//in = SinOsc.ar(440,0,0.1);
in= SoundIn.ar;

fft = FFT(LocalBuf(2048), in);

chroma=Chromagram.kr(fft, 2048, n);

//chroma=Chromagram.kr(fft, 2048, n, 36.midicps, 7, 1, 0.9);

Out.kr(0,chroma);
}.play;

c= Bus.new('control', 0, n);

)

//poll coefficients snapshot
c.getn(n,{arg val; {val.plot;}.defer});

//Continuous graphical display of Chromagram values; free routine before closing window

(
var ms;

w=Window.new((n.asString)++" chroma coefficients", Rect(200,400,n*20+50,300));

ms= MultiSliderView.new(w, Rect(10,10,n*20,280));

ms.value_(Array.fill(n,0.0));
ms.valueThumbSize_(20.0);
ms.indexThumbSize_(20.0);
ms.gap_(0);

w.front;

r= {

inf.do{

c.getn(n,{arg val; {ms.value_(val)}.defer});

0.04.wait; //25 frames per second
};

}.fork;

w.onClose = {
r.stop;
c.free;
x.free;
};

)

b.free;

//Bohlen-Pierce over 3 tritaves, normalized results per frame
(
{

var in, fft, chroma;

//in = SinOsc.ar(440,0,0.1);
in= SoundIn.ar;

fft = FFT(LocalBuf(2048), in);

chroma=Chromagram.kr(fft,2048,13,octaves:3,octaveratio:3,perframenormalize:1);

chroma.poll;

Out.ar(0,Pan2.ar(in));
}.play
)

helpfile source: source/SCMIRUGens/sc/HelpSource/Classes/Chromagram.schelp
link::sc3-plugins/Classes/Chromagram::

ChromagramExtension

Description

Class Methods

.kr

Arguments:

Examples

Chromagram
Extension