From the very beginning of the Nightwaves zine in 1999, one of my biggest supporters and contributors has been my good friend C.S. Graves. He shared his expertise on electronic music in a series of articles that he wrote which were subsequently published in the zine. On this page, I will dig into the vaults and feature some of his articles that he wrote. I hope to eventually feature all of his articles on this page, so keep checking back for additions.

CANCELLATION and INVERTED WAVEFORMS: The Sweet Sound of Silence

Written 1999/03/03

C.S. Graves

When two waveforms of equal and opposite amplitude meet, the result is a cancellation of both waveforms. Silence. Okay, I know what you're thinking. "How is that useful in making synthetic sounds?" A certain amount of cancellation can yield some interesting results.

For the purposes of this article, let's assume you have a sampler at your disposal (wavetable synths, alas, seldom have the option of inverting waveforms and thus will be excluded). Now suppose you have isolated a sample that can sustain for a long time. It can either be just a really long sample or a loop. Create a copy of this individual waveform that will play along with the original. If you play any key, you will basically hear the original sound except very loud. This is because the copy waveform is reinforcing the amplitude of the original. This is the opposite of what we want for our little experiment.

This is when you need to invert the copied waveform. This means the positive amplitudes will be turned negative and vice versa. If your sampler doesn't have such a feature, many audio editing programs for computers can perform this task, such as Syntrillium's Cool Edit or Creative's WaveStudio. Hopefully you have some way to convert or transfer the sounds back and forth from your computer to your sampler. There are sample-conversion programs for many brands, or if you've got the same format of digital input/output on both machines you're set. Now, whether you simply found the option on your sampler or you had to resort to the alternate kinds of trickery and witchcraft described above, you should have an inverted copy of the original waveform. And after all the fuss I've put you through so far you're probably itching to hear something cool. But before you discover that the steps thus far only produce total silence, and you swear I will feel your wrath for this, let me just say we're not quite finished yet.

The last step is modulation. Any difference in pitch, pan, or volume to either or both of the waveforms will undo the cancellation to various degrees. For example, try detuning one of the waveforms. You should hear sort of a phasing effect coupled with a slow attack. You could also set an envelope to change the volume of one wave, or pan the waves slowly in opposite directions (note that the panning method only works in stereo!). Maybe put on a subtle pitch LFO. Any modulations you can think of that will offset the two waveforms in time, amplitude, or stereo space will work.

Using inverted waveforms can make for great pad sounds, unique phasing-type effects, or breathe life into once sterile single-cycle loops. As usual, play with those parameters and see what magic you can work.

Velocity Range

Written 1999/07/30

C.S. Graves

"Daddy, what's velocity range?"

What is velocity range? A question a child might ask, but not a childish question.

Velocity is a form of MIDI data that measures the force with which the keyboard is hit, and represents this force with a number from 000 to 127 or 001 to 128, depending on the machine. Velocity range means that a certain waveform on a sampler or wavetable synth will only sound when velocity from the controlling keyboard falls within a specified range . For example, suppose a sinewave has a velocity range of 000-064. When the keys are hit hard with velocity values over 064 the sinewave will not sound, but when the keys are hit softly falling within the range, you will hear the wave.

Different voices or sample layers can occupy various velocity ranges, sounding separately or overlapping. Suppose now you also have a sawtooth that sounds only with velocities between 65 to 127. Depending on the force with which the keys are hit you will hear either a sine or a sawtooth. You can assign as many voices to as many ranges as your synth/sampler's architecture will allow.

Here's an example of how I applied this with a sampler to good effect. I cracked out my analog synth and setup a simple resonant sawtooth sound. Setting the low-pass filter cutoff quite low, I took a sample and looped it, then I set the velocity range from 000-015. After creating a new layer I repeated the process seven times, each time bringing up the filter cutoff a bit and assigning higher velocity ranges for the layers that didn't overlap the previous ones. I also disabled the effect of velocity on amplitude on all the layers, so that all the waveforms could be heard loud and clear at all velocities. When I was finished I had 8 layers, each containing a different looped waveform, and having these velocity ranges: 000-015, 016-031, 032-047, 048-063, 064-079, 080-095, 096-111, and 112-127. The result was a sampled instrument which produced resonant sawtooth waves with a cutoff point that seemed to increase with higher velocities. When played it has that "percolating" effect you hear in a lot of techno music, and sounds so sweet when you run it through delay!

I also used the procedure above for an istrument where the velocity triggered samples of an FM sound with different modulation indices instead of filter cutoff points.

Now that you've seen a few examples of how velocity ranges can be applied, you're free to imagine all sorts of velocity-sensitive instruments. And they don't have to be the memory-conserving, single-cycle loop-based sounds mentioned above. You can use more elaborate waveforms in your creation, be it purely synthetic or a realistic emulation, limited only by your sample RAM and/or polyphony.

A Beginner's Guide to FM Synthesis
Written 2000/01/06

C.S. Graves

Ever played an FM synth but have been too intimidated by all the esoteric terms and parameters to program your own FM sounds? Who hasn't? For years I would tinker with my Yamaha PSS-680, but that board really doesn't have the extensive parameters of synths like the DX series and other, more sophisticated, synths. It wasn't until Gary loaned me his DX-100 that I finally understood the basics of the standard Yamaha-style FM synthesis architecture (what other style of hardware FM synthesis is there?). Mind you, I'm obviously not John Chowning, but I think I've learned enough to help out anyone out there who might be trying to figure out how to get into creating their own FM sounds, but you're still going to need some basic knowledge of general synth terminologies (q.v. my article in Nightwaves issue 4, A Beginner's Glossary of Synthesis Terminologies).

As you may know, FM synthesis relies on one oscillator (the modulator) modulating the frequency of another (the carrier). What might throw some people off is that in Yamaha-style FM, oscillators are referred to as operators. Okay, no problem... now you want to establish how your particular synth displays which operators are active and which are affected by the parameters you will be fiddling with. For the DX- 100, there is a sequence of four digits on some pages to show which operators are active. The digits are either 1 for active, or 0 for inactive. The first digit will represent the first operator, the second represents the second operator, etc. For most parameters you should be able to use a certain button (possibly called operator select or something similar) to see the settings for that same parameter for each of the operators. The DX follows the parameter value with "1 OP", "2 OP", '3 OP", or "4 OP" which indicates what operator is currently selected for parameter editing.

Another of the cryptic things about Yamaha's FM synths is the various configurations to choose from. These are often graphically depicted on the synth itself for easy reference, but it doesn't do a lick of good if you don't know what it means. Here's how you can decipher these: choose one of the configurations (often a number will correspond with the graphic depictions) and then isolate a single operator to play on its own. If you hear a sinewave, then the operator you have selected is a carrier. Any operators that you cannot hear when you isolate them are modulators, unless you forgot to turn up the volume! As you do this, take note of where the carriers and modulators are shown in the diagrams for each configuration. This way you will be able to understand the configuration just by looking at the diagram and can pick the desired one for your patch. One last thing about these diagrams is an operator depicted with a line going out of, and back into, itself. This operator can utilize feedback, that is to say that it can be set to modulate itself to varying degrees. It is with this operator that sawtooth tones can be attained if you have the feedback and frequency ratio settings right.

So you've picked a configuration, now what? Well, now it would help to undestand the many parameters that will affect your FM sound. There are amplitude values that change the static volume of each operator. Take note that the volume of the modulators will have a dramatic effect on the carrier's timbre. This is called the modulation index.

Next is the frequency ratio. This is a value that represents the frequency of the operator relative to the default value (usually 1). So a ratio of .5 means the frequency is half that of an operator with a ratio of 1, and a quarter of that of an operator with a ratio of 2. Everytime the ratio is doubled, you move up an octave. In the case of the DX series there are a variety of preset ratios which the folks at Yamaha no doubt have determined to be most suitable for making musical sounds. This may seem limiting if you've used other hardware or software synths, and wish to tweak the modulators to xxx.xxxx hertz like in Visual Orangator, but you've got to work with what you've got. Try different combinations of carrier/modulator frequency ratios until something strikes your fancy. If they all sound harsh, try changing the modulation index, or just read on...

Using the synth's amplitude envelopes you make the overall volume and/or the modulation indices dynamic. This is where the real fun of making FM synth sounds begins. You can make a sound have a loud, harsh attack and then fade out to nothing. For this sort of thing you want the decay of the modulator to be quicker than that of the carrier. Or you could opt for an eerie pad sound that starts with gentle sinewave tones slowly being complexified by a modulator that increase in amplitude with the attack. These are just two examples of what the envelope section offers. Like any good sound designer (not that I qualify as such) EXPERIMENT!

You may also be able to assign an LFO to the amplitude and/or frequency of each operator. You can choose the type of waveform as well as how much the pitch or volume of the operator will be affected by it, adding even more comlexity and life to your sound.

To top it all off, many FM boards have additional parameters to allow modulation via velocity or breath controllers. While not many people are likely to use or even have heard of the latter, the velocity parameters can make the sound even more responsive if your Yamaha keyboard is velocity sensitive, or if it's being controlled through MIDI by one that is. For this reason alone I hope to get my hands on a used DX someday so that I might make shiny FM patches whose modulation indices are radically changed depending on how hard I hit the keys of the controller board.

That's all I can think of considering I don't have Gary's DX-100 sitting in front of me right now. I think I hit the important aspects of FM, though it may still seem a little esoteric until you get your hands into it and hear the results of the theory. I discovered that once you get past the obstacle of understanding the under-appreciated, non- subtractive, seemingly alien FM architecture, designing sounds for it will become as natural as with any other popular kind of synthesis. I hope that I've helped make that obstacle a little less daunting.

A BEGINNER'S GLOSSARY OF SYNTHESIS TERMINOLOGIES

written 1999/07/26

C.S. Graves

After having written my article on sample start modulation for issue one, it was suggested to me that I should have explained all the terms for the benefit of the uninitiated. I considered this, but concluded that it would have weighed down the article, and the constant digression into such explanations would have added further confusion to it. It would have to be assumed that my readers had a basic knowledge of synthesis for the piece to be quick and efficient. But the initial suggestion warranted an article of its own, and this is it. I will attempt to shed light on many of the most common technical terms used in synthesis today, so that the beginner may have some grasp on the concepts that will no doubt arise throughout the lifespan of this publication. You'll have to do a lot of jumping from one term to another and back again, so if you don't understand a word or two, look through the list and see if they are defined.

808 - from Roland's TR-808 drum machine. Often used to refer to the characteristic synthetic drums sounds produced by the 808.
Additive - the method of synthesis where numerous sine waves are added to a fundamental frequency. Theoretically any sound can be recreated using additive synthesis, but the sheer number of partials in a complex sound require tremendous computational power. The most familiar use of simple additive synthesis is in Hammond organs and the like.
ADSR - abbreviation for ATTACK DECAY SUSTAIN RELEASE. The prototypical envelope invented by Vladimir Ussachevsky for early Moog synthesizers.
Aftertouch - see Pressure.
Aliasing - in digital audio, the distortion that occurs when the frequencies of the source sound exceed the Nyquist frequency.
Amplitude - the extent or loudness of sound at any given time. Amplitude can be positive or negative.
Analog or Analogue - pre-digital method of synthesis that utilizes voltages to produce and process sound.
Analog Modelling - digital synthesis method designed to emulate analog synthesis.
Architecture - the setup and interaction of sound producing and processing components that dictates how sounds are synthesized on a given machine or piece of software.
Arpeggiator - a device which produces arpeggios at the touch of a key.
Attack - the initial stage of a sound. A fast or strong attack indicates immediacy, as in a loud burst of sound, while a slow or weak attack makes for a gradual increase, as in a crescendo or swelling.
Band-pass filter - a filter which only allows a defined spectrum of frequencies to pass.
Bit Resolution - the dynamic range possible in a digital audio format. The better the resolution, the more faithful the recording. Each bit rating is double the resolution of the rating immediately below it (8-bit = 2x7-bit)
Cancellation - when a positive and a negative amplitude cancel each other out.
Clipping - the distortion which occurs when the source sound exceeds the dynamic threshold of a digital recording.
Controller - either 1. a hardware device such as a keyboard used to control a synthesis device, 2. a component of a larger device used to control a specific aspect of the sounds, such as a mod wheel, or 3. a type of information sent by such devices or sequencers (e.g. velocity, volume, etc...).
Cross-fade - when one sound is faded out while another is faded in simultaneously. The intent is usually to create a seamless transition.
CV - abbr.: Control Voltage. Pretty self-explanatory. Control voltage is used to control some aspect of synthesis, such as pitch and filter cutoff on analog synths.
CV pedal - a control voltage pedal most often used to control volume, but can often be used to modulate other things.
Cycle - the smallest pattern within a waveform in which the amplitude starts at zero, travels through positive and negative values, and then returns to zero.
Decay - the stage in which some property of the sound decreases, such as the amplitude of a sound as it dies out.
Digital Synthesis - any method which relies on digital computers to produce sound.
DIN - pre-MIDI input/output standard for syncronizing drum machines and sequencers. Named for the 5-pin-DIN cable used to connect devices.
Drum Machine - device that produces drum sounds and rhythm patterns.
Duty cycle - in a pulse wave, the ratio of positive amplitude to wavelength expressed by a percentage.
Dynamic Range - the range between the softest and loudest sounds recordable by a medium.
Dynamic Threshold - the maximum amplitude recordable without distortion.
Emulative - synthesis intended to sound like, or emulate, a pre-existing instrument.
Envelope - a series of time values working in conjuction with modulation values. The ADSR evelope is the most well- known example.
Filter - to remove certain frequencies from a sound, or a device which performs this function.
Filter cutoff - the point where a filter ceases to affect sound frequencies.
FM - abbr.: Frequency Modulation. Method of synthesis where one oscillator modulates the frequency of another oscillator, called the carrier. Although technically even a low frequency modulator can be considered frequency modulation, the term FM is usually only applied when the modulator exceeds 30 Hz or so, and enters the audible range.
Gate - in analog synthesis, an audio signal which indicates when a key on the controller is being pressed and released. Gate controls the duration of notes played, much like MIDI Note on and Note off messages.
Hertz - a unit of measurement dealing with cycles per second, named after 19th century German physicist Heinrich Hertz. It can be used to express sound frequency and sample rate. It is subject to the prefixes used in the metric system (megahertz, kilohertz, etc...).
High-Pass Filter - a filter which removes low frequencies while allowing higher frequencies to pass.
Hz - see Hertz
LFO - abbr.: Low Frequency Oscillator. A modulator which when applied to pitch produces vibrato, and when applied to amplitude produces tremolo. LFO's can be any of the basic waveforms (see Sawtooth wave, Sinewave, Square wave, and triangle wave).
Loop - a section of a waveform that repeats itself. Loops are often used in sampling to conserve memory.
Low-Pass Filter - a filter which removes high frequencies while allowing low frequencies to pass.
MIDI - abbr.: Musical Instrument Digital Interface. A standard protocol invented in the 1980's to allow the interaction and control of multiple synthesis devices.
Mod Wheel - diminutive for Modulation Wheel. A wheel-like controller on a keyboard which can be used in performance to modulate elements of a synthetic sound. Most commonly used to control LFO depth.
Modular - method of synthesis where numerous modules are connected to produce sound. Modular synthesis has no fixed architecture and allows significant freedom for sound design. Most modular synthesizers are analog, but recently digital and software synthesizers have adopted the modular approach.
Modulation - to change any value or property of synthetic sound.
Monophonic - a synth where only one voice can sound at once.
Multitimbral - the ability of a synth to have multiple sounds play and be controlled separately.
Noise - a sound where various frequencies are present at any given time. White noise contains all frequencies, pink noise has less high frequencies than white, brown noise contains only low frequencies, and red noise is the result of white noise put through a band pass filter.
Nyquist Frequency - the highest frequency accurately reproduceable by digital means. It is one half of the sample rate of a digital recording.
Oscillator - a device which produces waveforms.
Pad - a gentle, sustaining sound often with a soft attack usually used to play chords in the background of a piece of music.
Pan - the position of a sound in stereo space.
Partial - one of the many pure tones (sinewaves) that make up a more complex waveform.
Patch - a synthesized sound, whether it's a single unprocessed oscillator, or many waveforms mixed together and heavily processed. The term comes from the patch cords used in modular synthesis.
PCM - abbr.: Pulse Code Modulation. Term indicating digital audio.
Physical Modelling - method of synthesis where mathematical algorithms are used to emulate the physical behaviour of acoustic instruments.
Polyphonic - a synth where multiple voices can sound at once.
Polyphony - the number of voices a device can play at once.
Preset - a patch or sound included with a synthesizer.
Pressure - the pressure exerted on a key after it is pressed.
Pulse wave - waveform where the transition from positive to negative amplitudes and back is very rapid. See also Square wave.
Pulse width - the length of the positive amplitude in a pulse wave.
Q - the bandwidth of a filter's resonance.
Quantize - the process of moving notes recorded into a sequencer to the closest time intervals specified by the user. Quantizing is used to correct rhythmic imperfections.
Release - the stage of a sound after a key is released. Sounds with a high release time end less abruptly than those with lower values.
Resonance - in filters, a function that reinforces frequencies near the filter-cutoff. Also used to refer to the Q setting. Resonance is perhaps what analog synthesis is best known for.
Sample - a digital waveform, or a patch made from such waveforms. Also, a single bit of digital audio information.
Sample-and-hold - modulation in fixed time intervals. The modulation can be random, or arpeggio-like.
Sampler - device that allows the user to create their own samples, or import samples created by others for use in composition and performance. This versatility has made samplers widely popular, and the method of choice for emulative synthesis.
Sample RAM - The amount of Random Access Memory present for storing samples in.
Sample Rate - in digital audio, the rate at which samples of the source sound are taken. Sample rate is most often expressed in kiloHertz (kHZ). The higher the sample rate, the higher the fidelity of the recording.
Sawtooth wave - basic waveform that contains all the harmonics in ever decreasing amplitude. It has a distinctive "buzzing" quality.
Sidebands - additional frequencies above and below the fundamental produced by FM synthesis.
Sinewave - the purest tone in sound, one of the basic waveforms. It contains no overtones.
Sequencer - device used to record and play back musical events, analogous to notation or piano rolls. Sequencers are used to control synthesizers to play music automatically to either accompany, or replace, the human performer.
Software Synthesis - any software program dedicated to producing synthetic sound. The term is most often applied to programs that can produce sound fast enough to be controlled via MIDI for performance or sequencer playback purposes.
Sound Module - a device designed solely to produce sound. It requires connection to a controller device to be played.
Square wave - a waveform with all odd harmonics. Technically it is a pulse wave with a duty cycle of 50%.
Subtractive - method of synthesis where frequencies are removed from a waveform rich in harmonics. Most methods in use today use subtractive synthesis via filtering.
Sustain - the stage of a sound that remains at a constant value after the decay as long as the key is depressed.
Sys Ex - diminutive for System Exclusive. This is information sent via MIDI intended to be used by only one device, but to be stored in another.
Theremin - Also known as the Etherovox, instrument invented in the 1920 by Lev Termin (Leon Theremin). The instrument is controlled by interruption of the energy field around a pitch antenna and an amplitude antenna. The player never touches the instrument during performance.
Tone Generator - term most often applied to Yamaha's FM sound modules.
Triangle wave - another of the basic waveforms. Contains odd harmonics in decreasing amplitude.
VCA - abbr.: Voltage Controlled Amplitude. The section of an analog synth that controls amplitude.
VCF - abbr.: Voltage Controlled Filter. The filter of an analog synth.
VCO - abbr.: Voltage Controlled Oscillator. The oscillator in an analog synth.
Velocity - the force with with a key is hit. In MIDI instruments, velocity can be expressed as a numerical value from 1-128.
Velocity sensitive - a keyboard that can record or transmit velocity information.
Voice - general term for either a single waveform or a single oscillator.
Waveform or Wave - the physical or digital shape of a sound.
Wavetable - a collection of samples stored in ROM. Also a synth containing such sounds.
Workstation - a combination of a controller keyboard, a sequencer, and a synthesizer. Many workstations include onboard effects processing.
Zero Crossing - point in a waveform where amplitude is at zero. Smooth loops should have beginning and end points at zero crossing.