User manual M-AUDIO TIMEWARP 2600

[. . . ] User Guide English 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 The TimewARP 2600 Manual . 3 1. 1 1. 2 1. 3 1. 4 The ARP 2600, 1970 - 1981 and Onward . [. . . ] Likewise, if the modulating signal--the program--is complex, the arithmetic applies separately to each of its components. 26 TimewARP · User Guide 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. 3. 6. 5. 2. 1 Ring Modulation While 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. Its output is simply the product, arithmetically, of the two 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 singlecomponent program, generates a three-component 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 inharmonic 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). In other words, the final spectrum has only as many components as the original program did. Picture the entire program signal spectrum shifted up or down by some fixed frequency. The important thing to remember about this is that it's not pitch shifting--which would have to be accomplished by frequency multiplication--but frequency shifting. It's an addition or subtraction process, and it really messes up any harmonic relationships that might have existed in the original spectrum. 3. 6. 5. 3 Frequency Modulation The spectrum resulting from amplitude modulation always has three components for every one component of the program signal: the carrier itself, and two sidebands. In Frequency Modulation, however, the number of sidebands depends on the modulation depth. It is possible from only two sine waves to generate a spectrum with dozens or even hundreds of components. Modulating one sawtooth with another can produce a spectrum so complex that it sounds almost like a noise generator. In such a patch, you will usually reach for a filter to take the edge off the resulting spectrum. What happens is this: as the depth of modulation increases, the number of sidebands does too, without limit. The additional sidebands come in at--guess what?--integral multiples of the program frequency. For this reason, the most useful FM techniques involve only sine-wave carrier and program signals. 3. 7 Controlling One Module by Means of Another The modulation methods we've just described can be accomplished with voltage-controlled or digitally-controlled equipment. For example, to set up an AM effect, feed the carrier signal into a VCA audio input, and the program signal into one of the amplitude-control inputs. [. . . ] C = 1/1 (260 Hz) 1/4 Tone Equal Temperament 24 notes per octave, equally spaced 24 root 2 intervals. Mexican composer Julian Carillo used this for custom-built pianos in the early 20th century. 19-Tone Equal Temperament 19 notes per octave, (19 root 2) offering better thirds than 12 ET, a better overall compromise if you can figure out the keyboard patterns. 31-Tone Equal Temperament Many people consider 31root2 to offer the best compromise towards just intonation in an equal temperament, but it can get very tricky to keep track of the intervals. [. . . ]