Compiling a Headless SC

The SC Linux build instructions are very detailed: https://github.com/supercollider/supercollider/blob/develop/README_LINUX.md Compiling it without all graphical components is straightforward. Simply add the flags NO_X11=ON and -DSC_QT=OFF for building a headless version of SuperCollider.

About JackTrip

In this class we will use JackTrip for audio over network connections but there were some successful tests with the Zita-njbridge. JackTrip can be used for peer-to-peer connections and for server-client setups. For the latter, JackTrip was extended with the so called HUB Mode for the SPRAWL System and the EOC in 2019-20.

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Starting JackTrip

$ jackd -d dummy [additional parameters]

$ jacktrip -S -p 5 -D --udprt

$ jacktrip -C server.address -n 2 -K AP_

Connecting to an SSH Server

For connecting to a remote machine, it needs to run an SSH server. On the client side, an SSH connection can be established without additional installations from the terminal on Linux and MAC machines and - since version 10 - from Windows. SSH receives the following command, with the remote user's credentials (username and ip-address). This user needs to be installed on the remote machine. The remote SSH server will ask for the user's password, if no SSH key has been installed.

$ ssh username@address

X11 Forwarding

X11, or the X Window System is a framework for a graphical user interface (GUI) environment, used on Unix systems. With X11 Forwarding, SSH can also be used to run applications with a GUI, remotely. When connecting to an SSH server from a Linux machine, simply add the -X argument to do so:

$ ssh -X username@address

$ ssh -X username@address

Remote Commands

SSH can also be used to send single commands, without starting a remote session. This example launches the jack_simple_client, which plays a continuing sine tone on the remote machine.

$ ssh -t username@address 'jack_simple_server'

Faust and Web Audio

Besides many targets, Faust can also be used to create ScriptProcessor nodes (Letz, 2015).

References

OpenWeatherMap

This first, simple Web Audio sonification application makes use of the Weather API for real-time, browser-based sonification of weather data. For fetching data, a free subscription is necessary: https://home.openweathermap.org

Once subscribed, the API key can be used to get current weather information in the browser:

https://api.openweathermap.org/data/2.5/weather?q=Potsdam&appid=eab7c410674e15bfdd841f66941a92c2

JSON Data Structure

The resulting output in JSON looks like this:

{
  "coord": {
    "lon": 13.41,
    "lat": 52.52
  },
  "weather": [
    {
      "id": 804,
      "main": "Clouds",
      "description": "overcast clouds",
      "icon": "04d"
    }
  ],
  "base": "stations",
  "main": {
    "temp": 9.74,
    "feels_like": 6.57,
    "temp_min": 9,
    "temp_max": 10.56,
    "pressure": 1034,
    "humidity": 93
  },
  "visibility": 8000,
  "wind": {
    "speed": 4.1,
    "deg": 270
  },
  "clouds": {
    "all": 90
  },
  "dt": 1604655648,
  "sys": {
    "type": 1,
    "id": 1275,
    "country": "DE",
    "sunrise": 1604643143,
    "sunset": 1604676458
  },
  "timezone": 3600,
  "id": 2950159,
  "name": "Berlin",
  "cod": 200
}

All entries of this data structure can be used as synthesis parameters in a sonification system with Web Audio.

Temperatures to Frequencies

The Result

The resulting app fetches the weather data of a chosen city, extracts temperature and humidity and sets the parameters of the audio processes:

What does the weather sound like in ...?

Enter City Name Stop

Beginnings of Computer Music

First experiments on digital sound creation took place 1951 in Australia, on the CSIRAC computer system. Besides from these experiments, the development of digital sound synthesis dates back to the first experiments of Max Mathews at Bell Labs in the mid 1950s. Mathews created the MUSIC I programming language for generating musical sounds through synthesis of a single triangular waveform on an IBM 704. The Silver Scale, realized by psychologist Newman Guttman in 1957, is one of the first ever digitally synthesized piece of music (Roads, 1980).

MUSIC and its versions (I, II, III, ...) are direct or indirect ancestors to most recent languages for sound processing. Mathews defined the building blocks for digital sound synthesis and processing in these frameworks (Mathews, 1969, p. 48). This concept of unit generators is still used today. Although the first experiments sound amusing from today's perspective, he already anticipated the potential of the computer as a musical instrument:

“There are no theoretical limitations to the performance of the computer as a source of musical sounds, in contrast to the performance of ordinary instruments.” (Mathews, 1963)

Mathews created the first digital musical pieces himself, but in order to fully explore the musical potential, he was joined by composers, artists and other researchers, such as Newman Guttman, James Tenney and Jean Claude Risset. Risset contributed to the development of electronic music by exploring the possibilities of spectral analysis-resynthesis (1:20) and psychoacoustic phenomena like the Shepard tone (4:43):

Later, the Bell Labs were visited by many renowned composers of various styles genres, including John Cage, Edgard Varèse and Laurie Spiegel (Park, 2009). The work at Bell Labs will be in focus again in the section on additive synthesis.

A Pedigree

The synthesis experiments at Bell Labs are the origin of most music programming languages and methods for digital sound synthesis. On different branches, techniques developed from that seed (Bilbao, 2009):

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The following family tree focuses on the tools used in this class and is thus without any claim to completeness:

Chowning & CCRMA

The foundation for many further developments was laid when John Chowning brought the software MUSIC VI to Stanford from a visit at Bell Labs in the 1060s. After migrating it to a PDP-6 computer, Chowning worked on his groundbreaking digital compositions, such as Turenas (1972), using the frequency modulation synthesis (FM) and spatial techniques. Although in particular known for discovering the FM synthesis, these works are far more than mere studies of technical means:

Puckette & IRCAM

Most of the active music programming environments, such as Puredata, Max/MSP, SuperCollider or CSound, are descendants of the MUSIC languages. Graphical programming languages like Max/MSP and Puredata were actually born as patching and mapping environments. Their common ancestor, the Patcher (Puckette, 1986; Puckette, 1988), developed by Miller Puckette at IRCAM in the 1980s, was a graphical environment for connecting MAX real-time processes and for controlling MIDI instruments.

The new means of programming and the increase in computational power allowed musique mixte with digital signal processing means. Pluton (1988-89) by Philippe Manoury is one of the first pieces to use MAX for processing piano sounds in real time (6:00-8:30):

Links

120 Years of Electronic Music is a very thorough site on history and development of electronic musical instruments.

A talk by Paul Davis (Jack, Ardour) on the development of open source audio:

References

Sending a SynthDef to a Server

SynthDefs are templates for Synths, which are sent to a server:

// define a SynthDef and send it to the server
(

SynthDef(\sine_example,
{
   // define arguments of the SynthDef
   |f = 100, a = 1|

   // calculate a sine wave with frequency and amplitude
   var x = a * SinOsc.ar(f);

   // send the signal to the output bus '0'
   Out.ar(0, x);

}).send(s);

)

Create a Synth from a SynthDef

Once a SynthDef has been sent to the server, instances can be created:

// create a synth from the SynthDef
~my_synth = Synth(\sine_example, [\f, 1000, \a, 1]);

// create another synth from the SynthDef
~another_synth = Synth(\sine_example, [\f, 1100, \a, 1]);

Changing Synth Parameters

All parameters defined in the SynthDef of running synths can be changed, using the associated variable on the client side:

// set a parameter
~my_synth.set(\f,900);

Removing Synths

Running synths with a client-side variable can be removed from the server:

// free the nodes
~my_synth.free();
~another_synth.free();

Audio to Control

Converting audio signals to control rate signals can be achieved with the snapshot~ object, as done in the example audio-to-control.pd. A possible application is an envelope follower. This object needs to be triggered to grab a snapshot, which is done with a metro object at 100 Hz in this example. The output is a level indicator for the LFO at 0.1 Hz:

Control to Audio

Usually, control signals can be connected to audio inlets. The conversion shown in the example audio-to-control.pd is thus less frequent. However, in some cases it might be necessary to convert control signals to audio rate. This is done with the sig~ object:

The Gain Example

The gain example is the entry point for coding on the PI system: https://github.com/anwaldt/sound_synthesis_pi

References