THE RAIN - Granular Texture Synthesizer
Yi Wu, Yongliang He
THE RAIN is a granular texture synthesizer VST plugin. It is our take on traditional granular synthesizer with a little twist. The randomization feature allow it to take a simple waterdrop sample and transform it into rich, rain like amorphous textures. The project is done with C++ and JUCE.
History of Granular Synthesis
I think it will be interesting to talk a little bit about the history of granular synthesis. Here is a little research Ning Yang, Aziz Ege Gonul and I did with Curtis Roads and his Granular Synthesis on MUSI 6003 Music Technology: History and Repertoire, a class I enjoy a lot.
Dr. Curtis Roads, born in 1951, is a computer music pioneer and famous microsound synthesis researcher. Roads currently serves as professor of Media Arts and Technology in UC Santa Barbara. In 1958, Xenakis composed concret PH as a first demonstration of granulation after developing gabor grain based on Dennis Gabor’s work on quantitative sound analysis. This new composing technique draws Roads’ attention when he attended Xenakis’ workshop in 1972 . Only three years later, Roads composed prototype, a very first computer generated music composing with granular synthesis method. In 1980, Roads composed his famous piece nscor. This piece proves the potential of utilization of granular synthesis for music improvising and opens research directions for microsound synthesis. After further development by Truax to endow real-time implementation to the granular synthesis, the method is realized in live performances. Today granular synthesis is very well known among the electronic musicians thank to the wide selection of supported software.
A. Early Roots
Technological implementation of first granular synthesis was made just after World War II by the Nobel Prize winner physicist Dennis Gabor. Before implementing a technological tool for granular synthesis, he developed a mathematical theory called Gabor Matrix. According to his theory, Fourier analysis is limited describing real-life events because it only covers infinite signals in time domain. Therefore, he fused frequency and time domain to represent sound event in a single Gaussian particle. In this way, he opened the doors of representing a sound as small overlapping grains, each of them lasting between 1 to 50 ms .
With Gabor’s innovation, electronic music studios quickly developed similar devices using Gabor’s technique in the following years. In France, Pierre Schaeffer and engineer Jacques Poullin build a granular sampler called Phonogene. It is followed by a German counterpart which is built with the help of the company called Springer. Historically this device is known as Tempophon, and it is used in the compositions of Herbert Eimert .
B. Gabor Grains
Iannis Xenakis followed the step of Gabor and consolidated his theories into “Grains of sound”, or simply as Gabor Grains , the elementary acoustica quanta defined by Gabor.
Xenakis composed Concret PH with granular techniques as early as 1958 in GRM studios. He used samples of burning wood to granulize sounds in his piece, which resulted in a crackling sound. A year later he focused more on granular synthesis to realize his piece Analogique A-B. He used stochastic methods heavily in combination with granular synthesis to create the piece. The term “grains of sound” coined for the first time during this piece and he is the first musician to develop a theory for sound grains to use in the compositional context .
Between 1975 and 1981, Curtis Roads experimented with digital computers to generate granular synthesis. Parameters of sound grains were entered into a punch card to control the computer and then computer recorded sounds to magnetic tape. This process was an offline synthesis, and he established a reasonably high sampling rate around 20 kHz with 12-bit resolution. Later, during the year 1981, he managed to increase the sampling rate to 40 KHz and used a 4-channel quadraphonic system for further experimentations. He used sampled sounds of percussions and saxophones to base his granular experimentation .
C. Technical Background and Realization of nscor
The core of granular synthesis consists of two elements: spectral content and envelope shape. Spectral content can be as simple as a sine wave or it can be sampled sounds. Spectral content can be accessed by time-stretching of the sampled sounds and then individual grains which are forming the sound can be can be used to create granular synthesis. The envelope part of the grains is related to the amplitude and time domain of the signals. They cover the start and end of the grain window and amplitude value of during the window time period .
Before Roads, the realization of granular synthesis: spectral content sampling, envelope shaping and organization of grains are all manually done on tape. It requires a great deal of labor if one considers controlling all the parameters for each of the grain. In 1975, Roads developed a compositional control program on a mainframe computer provides a solution for high level organization for the grains. The composer only requires to define a beginning set of parameters and after that the program will systematically generate the traits for each individual grain. With this program, the creation of nscor become possible .
nscor is realized in two distinct stages. The first stage consists of a subset of stages for synthesizing the sound material from different studios and the second stage consists of mixing and editing of the final material. The core fabric of the piece was derived from another piece called Objet which was also composed by Curtis Roads. Objet contains samples from Moog III analog synthesizer, a Buchla 100 Series synthesizer and a computer generated sounds from a computer. These sounds were all generated at UCSD and recorded on tape. After he recorded the sound materials, all the mixing and editing are done at MIT. Also note that not all parts of nscor use granular synthesis. He faded in granular parts during the editing process. For example, at around 0:35, he introduces sounds from VOSIM synthesizer and then around 0:41 mark he fades in a cloud of grains in the same register with the previous part. He then uses this fade-in and fade-out process in the following parts to introduce different granular clouds to make a transition between the sections of the piece.
A. Expansion of the Temporal Field
The main aesthetics of the granular synthesis is composition start from micro-time scale. The multiplicity of time scales in compositions have been acknowledged by composers for a long time. But the expansion of the temporal field to micro time scale was not appeared until 1930s. In 1937, John Cage envisioned the future that the composer will be faced the entire field of time, and the fraction of a second will be the basic unity in the measurement of time . With the availability of electronic devices such as reel-to-reel tape and wave generator in 1950s, composers are available to explore the territories of micro-time. Karlheinz Stockhausen and Iannis Xenakis were the first few people to explore the temporal limits of composition with tape splicing techniques. In Xenakis’s 1959 composition Analogique A-B, we can identify the micro-time aesthetics. Analogique A-B is one of the first granular synthesis composition . The piece was created with the idea that all sound is conceived as an assemblage of many elementary sounds adequately disposed in time so that we could synthesize sound in a similar manner – create sounds based on grains of micro-time samples grains . However, because of the technical limits of the time, their micro-time composition aesthetics, such as dense granular clouds texture, could not be fully realized until the dawn of computer synthesis.
B. Multiscale Approach to Composition
What differs Roads’ microsound granular synthesis aesthesis from early microsound pieces is the multiscale approach to composition. Roads states that operation on one-time scale could generate structure which might perceived on other time scale . In context of granular synthesis, one can work on the micro time scale to generate high-level musical structure. Xenakis predicted this approach in 1960, stated that each grain in the granular clusters represents not only a pure frequency but an already present structure of elementary grains . Roads took this idea and realized in nscor: a gradual change in particle duration results in timbre variations on the overall texture of the higher time scale sound. The piece starts with several sound objects and by manipulating single grains, Roads can achieve variety texture of the sound. With the multi-scale approach, the high-level texture of the sound could be manipulated not only by the organization of the grains in bigger scale, but also by changing the waveform, window, duration of the grain itself in micro-level . This approach combines top-down and bottom-up composition strategy, allows the composers to float freely across all time scale to maximize their creativity.
C. Opacity and Transparency
Roads also expands the mesostructure aesthetics of granular synthesis by introducing the idea of opacity and transparency. The particle density is used to describe numbers of grains in unit time. If the density of micro sonic event is sufficient, the temporal dimension appears to cohere and one will perceive it as a continuous clouds texture. This texture is described as opaque sound and tends to block out other sounds that shares its frequency range . However, by reducing the density, one can create a transparent cloud so that other sounds could hear through it. The aesthetics of controlling texture by particle density to organized layers of sound can be clearly heard in nscor, where sometimes the granular cloud is not so dense so that other layer of sound can come above it.
A. Impact on Technology
Curtis Roads granular synthesis method involves using general-purpose computer music systems for complicated calculations with non-real-time approach. Despite Road’s creation of nscor in 1980, the bottom-line of the method prevents other musicians from accessing neither the technique nor the resulting sounds. Nevertheless, there are a few musicians and researchers are inspired by Road’s granular synthesis method. They become his successors to develop better approach and extend the method’s publicity. One of the essential work is credit to Barry Truax with his study of a real-time implementation of granular synthesis in 1980s. . As described by Truax, the two major problems existed in Road’s granular synthesis methods are large data generation and control variable design. He used a DMX-1000 digital signal processor by Wallraff in 1979 to implement real-time granular synthesis with data generation. Four control variables, Center frequency and frequency range, offset number of samples from the start and offset range, average grain duration and duration range, delay time between grains, are designed for the users to determine the calculation of grain parameters. A few real-time control modes are also added to improve user interface during synthesis. With the developed approach, Truax composed Riverrun (1986), the first real-time granular synthesis realized piece. After the successful approach of the real-time implementation, Truax merged physical modeling ((Smith, 1992; Välimäki & Takala, 1996) and presented a diversified granular synthesis technique to create ecological sounds with sampled sound grains and meso-time control functions .
B. Impact on Aesthetics
From Roads to Truax, the granular synthesis with real-time capability achieved its first stage of completion. Road’s nscor also influences other composers with similar but different aesthetic approaches. Horacio Vaggione, who primary worked on micromontage , an area that shares similar concepts to granular synthesis, composed Schall in 1994 with a new direction in using graphical sound editors. Paul Lansky is another micromontage composer and under the influences of nscor, also created a few granular synthesis pieces, such as Idle Chatter (1985) . This piece shares same aesthetics of utilizing the opacity and transparency in the composition as Roads did in nscor. one can hear a dense granular cloud “evaporate” into more transparent texture fade into ambient background so that the vocal layer can be introduce into the front stage.
C. Impact on Future
Since the SynthO-Matic by James McCartney in 1990s, the granular synthesis method has been used in numerous computer programs. Truax used Csound to implement synthesis technique with his research study of environmental sounds . Xenakis built UPIC (Unite Polyagogique Informatique de CEMAMu) in 1977, and provided to Brigitte Robindore in 1995 to compose Comme Etranger et voyageurs sur la terre . Multiple granular synthesis programs are developed for functional usage. Mac-POD by Damian Keller and Chris Rolfe , AL & ERWIN by Rajmil Fischman , Granulab by Rasmus Ekman and Granulator by Nicolas Fourne  are a few of the representative programs. Some programing language such as Supercollider, Max/MSP are also compatible with granular synthesis.
From Gabor to Xenakis, and Roads to Truax, granular synthesis method has been widely used by hundreds of composers today. Both the increase of computing power and optimization in the software implementation have made the live performance of granular synthesis sound just as pre-recorded. Composers no long have to depend on huge computing systems and pre-calculate all the values to generate music pieces like Roads did in prototype and nscor, and neither do they have to obtain professional knowledges on microsound synthesis to compose or perform. Sufficient software programs, plugins and patches ensure the musicians to utilize granular synthesis method with minimized coding capabilities and bring computer improvised granular synthesis to the public.
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