Difference between revisions of "SuperCollider Tweets"

Revision as of 15:00, 1 July 2011

This pages analyses and explains some "tweet-size" SuperCollider examples.

"A popular way to share SuperCollider code is to post it to the social networking site Twitter. This site imposes a restriction on the length of posts, limiting them to 140 characters or less. Creating an interesting sound or piece of music within this constraint has proved a popular challenge."

[quoted from http://swiki.hfbk-hamburg.de:8888/MusicTechnology/899]

For more 140-character SuperCollider code, visit the link above. Feel free to contribute to this page with more analyses! [if you don't have edit access to this wiki, send it to ruviaro at stanford edu and I'll post it]

micromoog

// SuperCollider code analysis
// by Bruno Ruviaro, 2011-06-12

Server.default = s = Server.local.boot
g = SwingOSC.default

// Original SuperCollider tweet by 'micromoog'
// http://swiki.hfbk-hamburg.de:8888/MusicTechnology/899

play{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50))+(WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8)!2}

// I'll start with the second part of the code, after the 'plus' sign.

//
// SECOND HALF OF THE PATCH: right side of + sign
//

// Listen to a LFPulse turning on and off some white noise.
// Frequency is 1 Hz, so one noise burst per second ("quarter notes").
// Notice that we actually have half a second of noise, and half second of silence.
// This is because the default "width" of LFPulse is 1/2.
{WhiteNoise.ar(LFPulse.kr(1))}.play

// By controlling the width parameter we can then control the note duration.
// The examples below are still 1 Hz ("quarter notes"), but the actual durations are different:
{WhiteNoise.ar(LFPulse.kr(freq: 1, width: 1/10))}.play // note dur is 1/10 of the beat (very "staccato")
{WhiteNoise.ar(LFPulse.kr(freq: 1, width: 0.9))}.play // note dur is 9/10 of the beat ("non legato") 

// Now let's make this white noise pulsate 4 times per beat ("sixteenth notes")
{WhiteNoise.ar(LFPulse.kr(4))}.play              // standard staccato (width default = 0.5)
{WhiteNoise.ar(LFPulse.kr(4, width: 0.05))}.play // much more staccato for the hi-hats

// What if I wanted to have one of the white noise bursts to simulate a snare drum?
// One out of ever four would have to be longer. The width parameter has to change accordingly.
// We can use another LFPulse to do just that.

{LFPulse.kr(1, mul: 1/4, add: 0.05).poll(8, label: "out")}.play // outputs 0.05 and 0.3 for half a second each

// Simply plug the line above into the white noise:
{WhiteNoise.ar(LFPulse.kr(4, width: LFPulse.kr(1, mul: 1/4, add: 0.05)))}.play

// The beginning was a little off, so we adjust the iphase of inner LFPulse:
{WhiteNoise.ar(LFPulse.kr(4, width: LFPulse.kr(1, iphase: 3/4, mul: 1/4, add: 0.05)))}.play

// Abbreviate this to make it "twitter friendly". Note that we add '0' as the iphase of first
// LFPulse in order to avoid having to declare the keyword 'width' after, saving several characters...
// Also, the original code divides the whole thing by 8 to scale its global amplitude in the mix.
{WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8}.play

//
// FIRST HALF OF THE PATCH: left side of + sign
//

// This inner LFPulse outputs number 2 for three 'beats', then 4 for one beat (bpm: 60)
// LFPulse(freq, iphase, width, mul, add)
{(LFPulse.kr(1/4,1/4,1/4)*2+2).poll(4)}.play

// The LFPulse above controls the frequency of this LFSaw (2 or 4 Hz).
// With the mul/add, the LFSaw outputs a downward ramp from 70 to 30.
{LFSaw.kr(freq: LFPulse.kr(1/4,1/4,1/4)*2+2, iphase: 1, mul: -20, add: 50).poll}.play

// The LFSaw above controls the frequency of this LFCub. LFCub is more or less like a sine wave, different timbre.
// Thus we have a bass line glissando downwards from 70 Hz to 30 Hz; That LFPulse is controlling rhythm, then.
{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50))}.play

// Compare how the same thing sounds using a SinOsc instead:
{SinOsc.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50))}.play

//
// MIXING THE TWO PARTS TOGETHER
//

// Here's the first and second half of the code, still isolated:

{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50))}.play

{WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8}.play

// A simple '+' puts them together:
{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50)) + (WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8)}.play

// Note that the WhiteNoise has been enclosed in parentheses to force its division by 8 to happen *before* the sum.
// Listen to it without parentheses:
{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50)) + WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8}.play // without parentheses: white noise too loud!

// Now add a !2 at the end of the line to make it stereo...
{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50)) + (WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8)!2}.play

// Finally, to save ONE more character, put the 'play' in the beginning:
play{LFCub.ar(LFSaw.kr(LFPulse.kr(1/4,1/4,1/4)*2+2,1,-20,50))+(WhiteNoise.ar(LFPulse.kr(4,0,LFPulse.kr(1,3/4)/4+0.05))/8)}

// Done!

// Outstanding unanswered question: how come the inner LFPulse of WhiteNoise.ar produces THREE short notes
// and ONE longer note? Why is it not two short and two long? (even with the phase change...)

headcube

// =====================================================================
// SuperCollider code analysis
// Bruno Ruviaro, 2011-07-01
// Original tweet by Nathaniel Virgo (headcube)
// http://swiki.hfbk-hamburg.de:8888/MusicTechnology/899
// =====================================================================

{LocalOut.ar(a=CombN.ar(BPF.ar(LocalIn.ar(2)*7.5+Saw.ar([32,33],0.2),2**LFNoise0.kr(4/3,4)*300,0.1).distort,2,2,40));a}.play

// ********************************************************
// FIRST PART: INSIDE THE BPF
// ********************************************************

// Starting from the BPF, a bandpass filter.
// Below is a simple BPF filtering white noise.
// BPF.ar(in, freq, rq) --> input, center frequency, rq
// This example uses a fixed center frequency of 1000 Hz and a rq of 0.1:

{BPF.ar(WhiteNoise.ar(1), 1000, 0.01)}.play

// Now instead of a fixed center frequency, let's use a
// LFNoise0 to generate new center frequencies for the BPF.
// The LFNoise0 will output a new value between 500 and 5000
// twice per second in this example:

{BPF.ar(WhiteNoise.ar(1), LFNoise0.kr(2).range(500, 5000), 0.1)}.play

// Same thing as above, but now using 'poll' so we
// can see the new freqs values being generated:

{BPF.ar(WhiteNoise.ar(1), LFNoise0.kr(2).range(500, 5000).poll(2, label: "bpf-freq"), 0.1)}.play

// Same thing but now using single impulses (Impulse.ar)
// as the input of the BPF, instead of WhiteNoise. We use the *5
// at the end just to make it louder (too soft otherwise). Listen:

{BPF.ar(Impulse.ar(2), LFNoise0.kr(2).range(500, 5000).poll(2, label: "bpf-freq"), 0.1)*5}.play // filtered impulses

// Now let's step back for a moment. Compare the sound
// of a single impulse to that of a slow sawtooth wave:

{Impulse.ar(1)}.play    // hear it
{Impulse.ar(1000)}.plot // see it
{Saw.ar(1)}.play        // hear it (you hear the dip of the sawtooth from +1 to -1)
{Saw.ar(1000)}.plot   // see it

// Let's use a 1 Hz sawtooth wave as the sound input for the BPF filter.
// These filtered 'saw pops' have a very different timbre from
// the filtered impulse pops created earlier with Impulse.ar:

{BPF.ar(Saw.ar(4), LFNoise0.kr(4).range(500, 5000).poll(4, label: "bpf-freq"), 0.1)}.play // "saw pops" BPF
// compare to
{BPF.ar(Impulse.ar(4), LFNoise0.kr(4).range(500, 5000).poll(4, label: "bpf-freq"), 0.1)*5}.play // "impulse pops" BPF 

// Getting a bit closer to the original tweet...
// Let's have get the Saw.ar at 32 and 33 Hz:

{Saw.ar(33)}.play // the raw saw, mono [CAREFUL: LOUD!]
{BPF.ar(Saw.ar(33), LFNoise0.kr(2).range(500, 5000).poll(2, label: "bpf-freq"), 0.1)}.play // raw saw thru BPF

{Saw.ar([32, 33])}.play // two raw saws, stereo [CAREFUL: LOUD!]
{BPF.ar(Saw.ar([32, 33]), LFNoise0.kr(2).range(500, 5000).poll(2, label: "bpf-freq"), 0.1)}.play // raw saws thru BPF

// Now let's say we want the BPF frequencies to be
// in the range 18.75 Hz to 4800 Hz, which is the
// range of the original tweet (more on that later):

{BPF.ar(Saw.ar([32, 33]), LFNoise0.kr(2).range(18.75, 4800).poll(2, label: "bpf-freq"), 0.1)}.play

// Note that whenever the output of LFNoise0 produces a big leap from a very low to a 
// very high number (center frequency for BPF), there's a loud "pop" as a consequence.
// These are the interesting "accented notes" we often hear in the final result.
// Watch the Post window as you listen, and check when the louder pops happen.

// One more step closer to the original tweet:
// Let's make the LFNoise0 freq to be 4/3, that is,
// 4 new values every 3 seconds (note that we change
// the poll frequency accordingly):

{BPF.ar(Saw.ar([32, 33]), LFNoise0.kr(4/3).range(18.75, 4800).poll(4/3, label: "bpf-freq"), 0.1)}.play

/* What does this mean? If you think of this rhythm in a Tempo of quarter note = 60,
   which will be the case in the final result, you have something like this
   (imagine these are representations of 16th notes):

>  >   >   >
|||| |||| ||||
 
   In other words: the frequency of change of the BPF center-freqs (4/3 Hz)
   actually promotes a certain "syncopated" feel of the final result, especially 
   when the louder pops appear (created by the occasional sudden change from a very low 
   to a very high BPF center-freq)
*/

// Now take a look at how the scaling of the output of LFNoise0
// is actually accomplished in the original tweet. The author does
// use .range(18.75, 4800). Instead we see this:

2**LFNoise0.kr(4/3,4)*300 // output range is 18.75 to 4800 Hz

// With 4 as the "mul", the range of this LFNoise0 becomes -4 to + 4.
// "2 to the power of (-4 up to + 4), and this result multiplied by 300"

2**(-4)*300 // Evaluate this: if LFNoise0 outputs its lowest -4, result is 18.75
2**(0)*300  // Evaluate this: if LFNoise0 outputs its middle value 0, the result is 300
2**(4)*300  // Evaluate this: if LFNoise0 outputs its highest +4, result is 4800

// So, in fact, the range boundaries are the same as in our earlier examples
// using .range(18.75, 4800), but, unlike before, the distribution is NOT linear.
// Compare how often you see numbers below 300 appearing in these two examples:

{LFNoise0.kr(4/3).range(18.75, 4800).poll(4/3, label: "linear")}.play  // Watch the Post window
{(2**LFNoise0.kr(4/3,4)*300).poll(4/3, label: "exponential")}.play     // Watch the Post window

// You can see from the math above that, in the second case, the distribution
// of random values is not anymore linear. Basically, there's 50% of chance that
// the selected value will be BELOW 300; and 50% of chance that it will be above 300.
// In other words, lower center-freqs for the BPF are now being favored. 

// This is how the linear distribution sounds like with the rest of our code so far:

{BPF.ar(Saw.ar([32, 33]), LFNoise0.kr(4/3).range(18.75, 4800).poll(4/3, label: "bpf-freq"), 0.1)}.play

// And this is how the exponential one sounds like:

{BPF.ar(Saw.ar([32,33]),(2**LFNoise0.kr(4/3,4)*300).poll(2, label: "bpf-freq"),0.1)}.play

// The exponential one not only favors lower notes in general, but also 
// increases the likelihood of even louder pops to appear (leaps from
// very low to very high center-freq). That's probably why the original tweet
// uses a multiplier of 0.2 for the Saw:

{BPF.ar(Saw.ar([32,33],0.2),(2**LFNoise0.kr(4/3,4)*300).poll(4/3, label: "bpf-freq"),0.1)}.play

// Finally, a 'distort' method is added to this to smooth things out a bit:

{BPF.ar(Saw.ar([32,33],0.2),(2**LFNoise0.kr(4/3,4)*300).poll(4/3, label: "bpf-freq"),0.1).distort}.scope

// A few visual examples of what distort does:

{LFSaw.ar(300)}.plot          // sawtooth
{LFSaw.ar(300).distort}.plot  // sawtooth with distort

{SinOsc.ar(300)}.plot          // sine
{SinOsc.ar(300).distort}.plot  // sine with distort

{LFTri.ar(300)}.plot          // triangle
{LFTri.ar(300).distort}.plot  // triangle with distort


// Back to the tweet, inside the BPF. Here's the original tweet again:

{LocalOut.ar(a=CombN.ar(BPF.ar(LocalIn.ar(2)*7.5+Saw.ar([32,33],0.2),2**LFNoise0.kr(4/3,4)*300,0.1).distort,2,2,40));a}.play

// There is still this LocalIn.ar(2)*7.5+ in the code, 
// preceding the Saw, and which we have not analyzed yet.
// Forget about it for now. Let's look at the the CombN,
// which has the entire BPF code as its first argument.


// ********************************************************
// SECOND PART: CombN
// ********************************************************

// This is a comb delay line.
// CombN.ar(in, maxdelaytime, delaytime, decaytime, mul, add)
// Simple example with Impulses:

{CombN.ar(Impulse.ar(1/2), 2, 0.25, 3)}.play

// Input signal: one impulse every 2 seconds (1/2 Hz)
// Maximum delay time: 2 seconds
// Delay time: 0.25 seconds
// Decay time: 3

// You can hear the 'echoing' impulse fading out.
// Now let's plug that BPF code into a CombN:

{CombN.ar(
	BPF.ar(Saw.ar([32,33],0.2),(2**LFNoise0.kr(4/3,4)*300),0.1).distort, // input signal
	2, // max delay time
	0.25, // delay time
	3) // decay time
}.play

// Same thing, with longer decay time (10s), and delay of 1 second:

{CombN.ar(
	BPF.ar(Saw.ar([32,33],0.2),(2**LFNoise0.kr(4/3,4)*300),0.1).distort, // input signal
	2, // max delay time
	1, // delay time
	10) // decay time
}.play

// Now with the actual values used in the original tweet,
// that is, very long decay time (40s) and delay = 2 seconds

{CombN.ar(
	BPF.ar(Saw.ar([32,33],0.2),(2**LFNoise0.kr(4/3,4)*300),0.1).distort, // input signal
	2, // max delay time
	2, // delay time
	40) // decay time
}.play

// Because the delay is now 2 seconds, we hear it more as 'meter'
// rathern than 'echo'. The result is a kind of 2-beat metric structure
// (say, a 2/4 with quarter note = 60), which gradually gets filled
// with "sixteenth notes" (the 4:3 pattern of the LFNoise0)
// as the CombN accumulates decaying echoes of these attacks.

// Remember the earlier example with a linear distribution of the
// random numbers between 18.75 and 4800? If we use THAT one now,
// a lot LESS pops (attacks) are generated, and the whole thing is
// much less rhythmic as a result. The exponential distribution
// of random numbers is then directly relevant to the 
// effectiveness of the final rhythmic result. Here's how
// this same bit of code sounds with the linear distribution:

{CombN.ar(
	BPF.ar(Saw.ar([32,33],0.2),LFNoise0.kr(4/3).range(18.75, 4800),0.1).distort, // input signal
	2, // max delay time
	2, // delay time
	40) // decay time
}.play

//  Another variation below. A version with white noise instead of the
//  sawtooth reveals an interesting aspect about the sawtooth:

{CombN.ar(
	BPF.ar(WhiteNoise.ar([1,1]),(2**LFNoise0.kr(4/3,4)*300),0.1).distort, // input signal
	2, // max delay time
	2, // delay time
	40) // decay time
}.play

// We still get occasional "rhythmic" pops; but note that the distance
// in amplitude between the pops and the 'sustained' portions of
// the texture is smaller; the continuous white noise 
// competes for the foreground with the pops. In the original Saw
// version, the dynamic distance between 'explosive' pops and the
// continuous notes is much bigger, so that the pops (thus the rhythm)
// becomes clearly the foreground within an overall 'quieter' texture.

// Here's another version, back with Saw, but with a more limited
// range of center freqs for the BPF. The attacks (pops) disappear, since
// there are no more big leaps from low to high center-freqs. A more continuous
// texture becomes prevalent, but you can still hear the underlying rhythm:

{CombN.ar(
	BPF.ar(Saw.ar([32,33],0.2),LFNoise0.kr(4/3).range(500, 1500),0.1).distort, // input signal
	2, // max delay time
	2, // delay time
	40) // decay time
}.play


// ********************************************************
// THIRD PART: LocalIn and LocalOut
// ********************************************************

// LocalIn.ar and LocalOut.ar are internal buses (see help file).
// In the example below, we feed one impulse every 3 seconds
// into this local bus. LocalIn is inside LocalOut, thus a feedback
// is created. The impulse is repeated every 64 samples (block size),
// each time multiplied by 0.99 (so it fades out quickly).

{LocalOut.ar(a=LocalIn.ar(1)+Impulse.ar(1/3)*0.99);a}.play

// Assuming the current sampling rate (sr) is 44100, we can find out the
// frequency of this "note" by dividing sr by 64 (block size):

44100/64  // result is 689.0625 Hz if your sr = 44100

// Check it with a sine wave, they should sound the same pitch:

{SinOsc.ar(44100/64, mul: 0.5)}.play // freq = sampling rate / block size

{LocalOut.ar(a=LocalIn.ar(1)+Impulse.ar(1/3)*0.99);a}.play // freq = sampling rate / block size

// The variable 'a' above works like in the simpler example below.
// There are two statements separated by a semicolon:

{a=SinOsc.ar(440);a}.play

// Finally, this is how the original tweet
// uses the LocalIn LocalOut structure:

{LocalOut.ar(a=CombN.ar(BPF.ar(LocalIn.ar(2)*7.5+Saw.ar([32,33],0.2),2**LFNoise0.kr(4/3,4)*300,0.1).distort,2,2,40));a}.play

// The variable 'a' is the CombN code we analyzed earlier:

{CombN.ar(BPF.ar(Saw.ar([32,33],0.2),2**LFNoise0.kr(4/3,4)*300,0.1).distort,2,2,40)}.play

/*

I still haven't figured out:

a) What exactly happens when the LocalIn / LocalOut structure is used?
b) Why is LocalIn.ar(2) multiplied by 7.5?

*/

mathk

// Original tweet by mathk
// http://swiki.hfbk-hamburg.de:8888/MusicTechnology/899

{k=LFNoise1.kr(8.0.rand+2,0.5,0.5);SinOsc.ar([[333,444],[222,555]]*(k+(rrand(1.0,5.0))),0,k).sum.cubed * 0.1}.play
// #supercollider #babies

mutantsounds

// Original tweet by mutantsounds
// http://swiki.hfbk-hamburg.de:8888/MusicTechnology/899

{x=Array.fill(5,{[0.00001,0.03].asSpec.map(LFNoise2.kr(3))});Splay.ar(Friction.ar(LFTri.ar(50),friction:x,mass:x*30000))}.play