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Tutorial 0: Granular Basics

Here's a good place to start if this is your first excursion into the world of granular synthesis. This tutorial is divided into 3 sections:

Making your first bleep: how RTGS3 generates sound

Step 1

Launch the RTGS3 application and start its audio engine by clicking the "Power On/Off" button so that it burns red:
PowerButton

Step 2

Open up the Buffers window by clicking the "View Buffers..." button:
ViewBuffersButton

The Buffers window is where RTGS3 stores its audio data for granulation. You'll notice that there are two empty waveform displays here, which means that you can work with two separate source sounds at the same time. For the purpose of this tutorial we're going to fill these buffers with a sine wave.

Step 3

In the Buffers window, open the Generate Audio window by clicking either of the "Fill Buffer..." buttons:
FillBufferButton

Step 4

In the Generate Audio window, set the "Data to Write" menu to "Sine Wave", the "Amplitude" slider to 75%, and the "Frequency" to 220. Hz. Then click the "Generate" button and watch as your buffer gets filled up with audio data:
TheGenerateAudioWindow

Step 5

Repeat steps 3 and 4 for the other buffer.

Step 6

Close the Generate Audio and Buffers windows, and return to the main RTGS3 interface window.

Step 7

Click the "Generate a Grain" button:
GenerateaGrainButton

You should have heard a bleep from your speakers. If you didn't, then make sure your audio hardware is set up properly and that RTGS3 is using the correct driver. See the System Setup Section for more information and help.

Step 8

Move the Grains "Length" slider all the way to the right, and click again on the "Generate a Grain" button:
GrainsLengthSetHigh

This time, the bleep you heard was longer. In fact, if your settings match the image above the length of the bleep you heard would have been somewhere between 170 and 200 milliseconds long (about 1/5th of a second). In the next section, we'll look at how different parameter settings affect the sound of individual grains.

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Microsounds: getting to know the grain

Grains generated by RTGS3 can be long or short, loud or quiet, transposed high or low, and panned anywhere in the stereo spectrum. We've already seen how changing the Grains Length slider affects the length of the grain generated. Now let's look at some other sliders.

Step 1

It shouldn't come as a big surprise that by moving the Grains Amplitude slider to the left the grain becomes quieter. But have you noticed that there's a slightly transparent red region surrounding some of the RTGS3 sliders? This region shows the amount of randomness associated with that slider's setting, and this randomness is key to understanding the power of granular synthesis technique. By clicking on the "R" next to the Grains Amplitude slider you'll see this region turn white, and now you can change the amount of randomness with the mouse:
GrainsAmpSetRange

Click the "Generate a Grain" button a few times. If your Grains Amplitude slider is set similar to the image above you should notice a distinct difference in the loudness of each grain generated.

Step 2

Now the fun starts. Find the Transposition slider and click the double outward arrows icon just below it:
TransMaxRange

Clicking the double outward arrows button automatically sets the random range of that slider to its maximum. Now if you click the "Generate a Grain" button you'll hear that each grain is transposed by some random value. Tutorial 4 will cover the Transposition slider in more detail.

Step 3

Sometimes you want lots of randomness, and sometimes you don't. Find the Panning slider and click the double inward arrows icon just above it:
RandMinRange

Clicking the double inward arrows button automatically sets the random range of that slider to its minimum. Now if you click the "Generate a Grain" button you'll hear that each grain is panned exactly in the centre.

Step 4

You may have noticed that the bleep we've been generating fades in and out quickly, instead of just starting and ending at full volume. This is thanks to the Grain Envelope, whose function it is to provide a smooth amplitude curve for each grain we generate. You'll notice that the Grain Envelope has some controls associated with it, including a 2D slider and menu:
GrainEnvelope

Try changing the Grain Envelope menu to "Triangle" and then drag the 2D slider knob all the way to the bottom-left corner. Click "Generate a Grain" a few times to get an idea of what you've just changed. Now drag the 2D slider knob all the way to the bottom-right corner and you'll hear a substantial difference in the grain's amplitude envelope. (If you find the difference difficult to detect, try setting the Grain Length slider so that the grains are longer than 100 milliseconds.)

Step 5

Now might be a good moment to experiment on your own for a few minutes. Why not go back to the Generate Audio window and fill your buffers up with white noise? Or how about filling one buffer with noise and the other with a square wave? In the next section we'll load some more interesting sounds into the buffers and see how great the potential of granular synthesis can be.


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Let's get thick: granulating a soundfile

There's a lot of fun to be had processing synthesized sounds in the manner described above, but it's more likely that you've been attracted to granular synthesis because of the rich, dense sonic landscapes that are characteristic of this technique. Let's now then take a look at a more typical way of generating sound with RTGS3.

Step 1

Go back to the Buffers window and click one of the "Read File..." buttons:
ReadFileButton

A standard Macintosh Open dialog window will open. Locate the file "ScratchThumpPiano.aif" in the RTGS3Help folder and select it. Load this file into the other buffer as well, so that the same audio file is in both buffers.

Step 2

Close the Buffers window and return to the main RTGS3 interface window. Move the sliders back to their default state and set the Grain Envelope back to "Cosine" with the 2D slider to the top-centre position:
MainSlidersDefault GrainEnvelope

The RTGS3 default settings are a good starting point for processing audio recordings.

Step 3

Turn on automatic grain generation by clicking the Grains On/Off toggle switch:
GrainsToggle

What you're hearing are grains of sound taken from the first 30-90 milliseconds of the source sound, generated once every 5-15 milliseconds.

Step 4

Drag the Buffer Position slider slowly, starting from the leftmost position (0 ms) and stop at 600 ms:
BufferSliderat600

Scrubbing slowly across a sound sample like this is a great way of discovering what might be called the "inner complexity" of a sound, and it has been used extensively by composers such as Barry Truax and Craig Vear.

Tip: for more accurate control of any of the RTGS3 sliders, hold down the SHIFT key while dragging. This is especially useful for the Buffer Position and Transposition Amount sliders.

Step 5

Keep the Buffer Position slider at 600 ms and adjust the randomness factor of the Transposition Amount slider. Remember that to do this you must first click the "R" icon next to the slider:
TransSetRange

Tip: you can also set the randomness factor of any slider by holding down the CTRL key before clicking on that slider.

In this tutorial we covered the essential technical aspects of granular synthesis and discovered how different kinds of sounds can be made using RTGS3. In the next tutorial we will examine all the features of the RTGS3 sliders in detail.

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