User manual WAY OUT WARE TIMEWARP 2600

[. . . ] OWNER'S MANUAL Owner's Manual Copyright © 2004, by Way Out Ware, Inc. . No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, from or to any form of media, without the prior written permission of Way Out Ware, Inc. . Requests for permission to reproduce any part of this work should be addressed to : Way Out Ware, Inc. , attn: Copyright Adminstration, info@wayoutware. com. Table of Contents 1 1 The ARP 2600, 1970 ­ 1981 and onward. . . 1 2 System Requirements, Installation, Configuration, Setup and Usage . [. . . ] The first two are more commonly used in audio synthesis than the third; we won't say anything here about phase modulation. Using AM and FM methods, it is possible to generate waveforms and spectra that are far more complicated ­ and interesting to the ear ­ than anything that can be produced by merely mixing and filtering signals. Mainly that is because of sidebands. 23 CHAPTER 3 - The Craft of audio Synthesis 3. 6. 5. 1 Sidebands and Sideband Spectra What happens to the spectrum of a sine wave when we modulate its amplitude?Clearly, since the signal that results from AM or FM methods is no longer a plain vanilla sine wave, then, in the frequency domain, it must have some additional components. They have been studied for at least a century, and are pretty well understood physically and mathematically. Audio synthesis is probably the only application of AM or FM modulation where we are interested in sidebands for their own sake, as something to listen to directly; in the past, this stuff was only interesting to radio engineers, radar, sonar, television broadcast engineering. In those disciplines, modulation sidebands are products of broadcasting methods, in the electromagnetic spectrum. Because of that historical background, some of the conventional language for talking about modulation processes is a little weird: the signal being modulated is often referred to as the carrier signal, and the signal that signal provides the modulation pattern is called the program. and this for a program program spectrum here's the AM result: lower sideband carrier weakend upper sideband Any form of modulation generates, for each component of the original signal, at least one lower sideband ­ at a frequency equal to the component minus the modulating frequency ­ and at least one upper sideband, at a frequency equal to the component plus the modulating frequency. If the carrier ­ the original signal - is itself complex, with multiple spectral components, then each of its components will produce its own sidebands independently of all the others. Likewise, if the modulating signal ­ the program - is complex, the arithmetic applies separately to each of its components. So, just for example, if you modulate a 10-component carrier signal with a 10-component program signal, the signal resulting from the modulation will have not less than 100 spectral components. This can get very messy; the most useful thing you can do with such a signal, before you do anything else, is filter it to get rid of some of the fuzz. here's the ring modulation: the carrier is gone ? and here's the FM result: variable number of sidebands and varying amplitude depending on the modulation depth 3. 6. 5. 2 Amplitude Modulation Suppose we modulate the amplitude of a 1000Hz sine wave with a 5Hz sine wave. The result is indistinguishable from what we would get if we mixed three sine waves, at 995Hz, 1KHz, and 1005Hz. The 995Hz component of the output is the lower sideband resulting from the modulation, and the 1005Hz component is the upper sideband. 24 CHAPTER 3 - The Craft of audio Synthesis 3. 6. 5. 2. 1 Ring Modulation Whereas a VCA responds only to a positive-going signal at its amplitude-control input, a ring modulator responds to both positive and negative levels at both of its inputs. If you are new to audio synthesis, draw a couple of signal graphs ­ it doesn't matter what they are ­ on the same timebase and vertical scale, and use a pocket calculator to work out the result of multiplying the two signals together. (The expression "ring modulator" describes the appearance of the analogue circuit design that's required for the multiplication. ) In the frequency domain, the difference between this and ordinary AM is only that the carrier signal components are suppressed. Once again, if you work out the arithmetic, a single-frequency carrier, modulated by a single-component program, generates a threecomponent AM spectrum but only a two-component ring-modulation spectrum. Well, since the carrier is almost always periodic (it comes from an oscillator, right?), it has a harmonic spectrum. Suppressing this spectrum lets you hear just the sidebands, which can be completely enharmonic if you're careful about the ratio of the two input signal frequencies. 3. 6. 5. 2. 2 Frequency Shifting It's theoretically possible not only to suppress the original carrier, as in ring modulation, but to isolate the lower and upper sidebands and make them available separately. The arithmetic here is fascinating, because the end result (for once) is in one-to-one correspondence with the input: for each component of the program signal, there is a component in the output at C-p (or at C+p). [. . . ] If you are new to audio synthesis, consult the tutorial patch collection. Appendices 6 6. 1 Table of Alternate keyboard tunings Tuning Presets, compiled by Robert Rich 6. 1. 1 12 Tone Equal Temperament (non-erasable) The default Western tuning, based on the twelfth root of two. Good fourths and fifths, horrible thirds and sixths. 6. 1. 2 Harmonic Series MIDI notes 36-95 reflect harmonics 2 through 60 based on the fundamental of A = 27. 5 Hz. The low C on a standard 5 octave keyboard acts as the root note (55Hz), and the harmonics play upwards from there. The remaining keys above and below the 5 octave range are filled with the same intervals as Carlos' Harmonic 12 Tone that follows. 6. 1. 3 Carlos Harmonic Twelve Tone Wendy Carlos' twelve note scale based on octave-repeating harmonics. [. . . ]