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| The Basics of Synthesis and Sound Programming Written by Len Sasso - © 2005, PRIMEDIA Business Magazines & Media Inc. Reprinted with Permission. |
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In this article, I'll take an operational approach to synthesizer programming by exploring the quickest route to customizing factory presets. Our starting point will be the General MIDI (GM) sound set, which contains 128 sounds covering all of the basic categories. Most synths and many samplers contain a bank conforming to the GM standard. But if that doesn't include your model, you can still follow along, because everything I cover here will apply in almost any context. One thing you will definitely need is a programmable instrument of some sort. That can be a hardware or software synthesizer or sampler of just about any design. If you only have a preset synth (such as the Yamaha CBX-K1XG), you may still be able to get some mileage out of it if it allows MIDI or built-in controllers to alter basic preset parameters. I'll refer to that option as we go along. Getting Under The Hood The first thing you need to do — which is also often the biggest hurdle to overcome — is to learn how to get into your module's patch or program editor and find the various settings you want to adjust. If it's a hardware synth of fairly recent vintage, it will probably have an LCD, an array of buttons for navigating various modes and menus, and one or more knobs for adjusting settings. If you're lucky enough to have a large LCD screen or a software editor that runs on your computer, things will be much simpler. If not, there's unfortunately no way around stepping through multiple menu layers trying to decipher cryptic parameter names like “VDA1 EG” and “AT41 AL99 DT93.” Needless to say, your manual is your friend — it's your only way under the hood. Here are a few things to look for as you browse through your unit's documentation. If your synth has several modes of operation, find out how to select the mode that plays a single sound on a single MIDI channel while editing. That is often called Patch or Program mode. Once in that mode, you will need to enter the program editor, for which there is typically an Edit button. In the editor, you'll need to learn how to step through menu pages to find the parameters you want to edit, how to move among the multiple parameters that occupy the same page, and how to change selected values. There are always buttons or knobs dedicated to those functions, and using them will quickly become second nature. Most hardware models store a large number of factory programs in ROM (that can not be edited) and have a smaller user area of RAM for programs you create. You will need to dip into the manual to learn how to move, copy, and save programs in the user area. Otherwise, all your hard work will be wiped out when you turn the machine off. If you're working with a software device, you need to remember to save your work — preferably to a new location or using a new name so you don't overwrite the original program. Pushing The Envelope The quickest and easiest way to change the character of a sound is to alter its amplitude envelope. One way to think of an envelope (also known as an “envelope generator” or “contour generator”) is as a type of built-in automation that is initiated whenever a note is played. Envelopes can be used for many things, one of which is to control the amplitude (loudness) of the sound being played. Envelopes can be described in terms of stages consisting of levels and times to reach those levels. The most common envelope — and the kind that is usually used for amplitude — has four stages, named Attack, Decay, Sustain, and Release (ADSR for short). In its simplest form, an ADSR envelope has four user settings: attack time, decay time, sustain level, and release time. The other four settings are fixed: the attack level is the maximum envelope level; the decay level is the same as the sustain level; the sustain time is the time that the note is held down; and the release level is zero. In short, when a note is played, the sound rises to its maximum level then falls to the sustain level where it stays until the note is released. The sound level then falls to zero in the release time. A more intuitive way to picture an envelope is by its shape. Software editors and hardware devices with large LCDs usually allow you to edit envelopes graphically, making the process much simpler. But even if you are consigned to doing it numerically, it's well worth exploring the envelope settings your equipment offers. For example, starting with a piano sound (GM preset 1) and reducing the decay time produces a damped-string effect. Increasing the release time simulates playing with the sustain pedal down. Reducing the decay time to zero and increasing the attack time significantly gives a reverse-piano effect. Increasing the sustain level to maximum and increasing the attack time a little yields a bowed-string sound. (If you're working with a preset-only synth, MIDI Control Change messages 72, 73, and 80 can often be used to control the release, attack, and decay times.) Audio Example 1 uses four sounds derived from a piano program by modifying only the amplitude envelope. Modern synths, especially software ones, often extend the basic ADSR concept in two ways: they provide more stages and they offer control over the shape of each ramp. With the exception of the Organ, the envelopes pictured in Fig. 1 all have curved ramps, which best match the behavior of acoustic instruments. Many synths allow MIDI Note Velocity to affect both the envelope levels and times. That allows you to play much more expressively using your MIDI keyboard. With piano sounds, for example, having the attack level (or the overall envelope level) and the decay time increase for higher Velocities gives a more realistic keyboard feel. This is an excerpt from the following article: Synth Programming 101. To stay informed about new articles, be sure to click here to sign up for the DigiFreq Music Technology Newsletter. It's free!
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