Introduction

Many sound modules offer you the ability to create your own patches. If the sound module is a MIDI sampler, then you can typically load new waveforms into it for use in your newly created patches.

But other sound modules, whereas they do allow you to create your own patches, do not offer the ability to load new waveforms. They have a limited selection of waveforms burned into a ROM chip. You can layer these waveforms in one patch, and process them a bit to alter their tonal qualities, thereby creating a new "sound" for that patch. Often, the selection of waveforms include waveforms that may not be useful on their own, but when layered with other waveforms, better help to simulate the characterics of some acoustic instrument. For example, there may be a "breath noise" waveform, which is meant to be layered with some other waveform to create a patch that sounds like some sort of woodwind or brass instrument. This article gives you tips on how to best create patches that simulate real, acoustic instruments upon such a sound module.


Select the right waveform

Of course you should first select a waveform that has some properties of the instrument you want to mimic. That's the first, important step. For example, if creating a flute patch, don't select a snare drum waveform as your "base" waveform. That sort of waveform (ie, an unpitched, extremely percussive waveform) has entirely different properties than a flute (ie, a pitched, wind instrument).

Go through the raw waveforms, and audition them. When I say "raw", I mean that you need to turn off any extra processing applied by the Voltage Controlled Amplifier (VCA) or Voltage Controlled Filter (VCF). You also want to turn off any Low Frequency Oscillator (LFO) effects.

To do that, set the VCF's Cutoff Frequency reasonably high. Turn off the VCF's Envelope Generator, as well as any "Keyboard Tracking" applied to the VCF's Cutoff Frequency. Also, make sure that any LFO is not directed to the VCF (Cutoff Frequency or Envelope Generator).

Do the same for the VCA. Turn off the VCA's Envelope Generator, as well as any "Keyboard Tracking" applied to the VCA's Level (or Volume). Also, make sure that any LFO is not directed to the VCA (Level or Envelope Generator).

This ensures that you're hearing the raw waveforms without extra processing (that you'll add later to tweak the sound for any even closer resemblance to the desired instrument).

Listen for properties that are applicable for the desired instrument. For example, a flute is a wind instrument. That means that it has a slower attack. (ie, It takes awhile for the musician to build up wind pressure inside of the instrument when sounding a note. By contrast, a pick on a guitar produces a note faster. We're talking about subtle time differences, but the human ear can percieve them, and that's one clue that our brain uses to distinguish between the sounds of instruments). Avoid waveforms that are clearly percussive (ie, sound like "plucked" instruments or are stuck with a mallet or stick, etc). Also, look for a waveform that seems to have some "breath noise" to it since that's another property of a wind instrument. (ie, There is a bit of randomness to the tone of an instrument whose sound is produced by a column of air generated by a breathing human. By contrast, a piano's tone is a lot less random after the initial hammer strike on the string. The string settles into a rather stable vibration).

So, for example, if you were making a mandolin patch, you'd instead be looking for some waveform whose initial attack makes it sound like it's a "plucked" instrument and has no breath noise. And you'd want a waveform that is pitched. (ie, You hear it as a distinct note, rather than something like a snare waveform which tends to sound like it's not tuned to a specific pitch).


Apply Filtering

Then learn what filtering does (ie, contours the timbre -- the overtones -- maybe even the "brightness" if you will). For example, lowering the VCF Cutoff Frequency makes the tone less bright and reduces the amount of overtones. Instruments that have strong overtones, such as a violin, may use a much higher Cutoff Frequency than instruments with less overtones such as a flute or clarinet.

Also recognize the importance of the VCF's Envelope Generator (EG). It contours the tone over time. (Technically, it raises and lowers the Cutoff Frequency while the waveform is playing. Therefore, think of it as a setting for when the waveform gets "brighter" or "darker"). Typically, most EG's have 4 stages. An initial "attack stage" is the brightness level when you first sound the waveform. Each stage usually has two settings -- the brightness level, and a time setting. Depending upon which stage it is, the time setting may determine how long it takes to go from the previous stage's brightness level to this brightness level, or perhaps how long it takes to go from this brightness level to the next stage's brightness level.

For example, you can have the initial attack of the waveform start out really bright, and then *quickly* fade to a darker sound (ie, a lower brightness level of the second stage). This accentuates the "pluck" of a waveform, so you can make a waveform have a more pronounced pick sound to enhance its effect as a plucked instrument. To do this, you'd set the first stage's (brightness) level very high. You'd set its time very short (probably even 0). The time for the first stage determines how quickly the sound rises to that first brightness level. You want this as fast as possible because a plucked sound starts out with a very "sharp", bright attack... immediately. There's no "fade-in" on the brightness of that attack. You'd set the second stage's brightness a lot lower (so the sound darkens) and set it's time also very short. The second stage's time determines how quickly the brightness goes from the first stage to the second stage. For a plucked instrument, you want the brightness to quickly go from that first, very bright "pick pluck" sound, to the darker sound of the vibrating string.

On the other hand, wind instruments have slower attacks, as the musician's breath pressure builds up. And the act of blowing air into a wind column doesn't produce as "bright" an attack. So, your EG settings for a wind instrument may not have as high a level for the first stage. And you'll have a longer time for that first stage. So, the sound will have a slower "fade-in" on the brightness. And the second stage's brightness maybe won't be so much lower than the first stage's brightness. After all, the building wind pressure may cause an initial "peak" in the brightness, but it's not nearly as pronounced as with a plucked string. So there won't be as quick, and wide a change in the brightness between the first and second stages.

Applying keyboard tracking to the VCF's Cutoff Frequency allows you to have the sound get brighter when you play more forcefully, or darker when you play less forcefully. This can be very important for mimicking the characteristics of instruments since the tone of many instruments varies the "harder" or "softer" you play it.

Setting up the VCF is critical in getting the right "sound".


Apply Volume Contouring

The Voltage Controlled Amplifier (VCA) is also equally important. In particular, the VCA's envelope generator is key to mimicking an instrument. The VCA EG determines how the volume changes over time. (Technically, it raises and lowers the VCA level while the waveform is playing. Therefore, think of it as a setting for when the waveform gets "louder" or "softer"). Again, this EG usually has 4 stages. An initial "attack stage" is the volume level when you first sound the waveform. Each stage usually has two settings -- the volume level, and a time setting. Depending upon which stage it is, the time setting may determine how long it takes to go from the previous stage's volume to this volume, or perhaps how long it takes to go from this volume to the next stage's volume.

For example, you can have the initial attack of the waveform start out really loud, and then *quickly* fade to a softer sound (ie, a lower volume of the second stage). This accentuates the "pluck" of a waveform, so you can make a waveform have a more pronounced pick sound to enhance its effect as a plucked instrument. To do this, you'd set the first stage's volume very high. You'd set its time very short (probably even 0). The time for the first stage determines how quickly the sound rises to that first volume. You want this as fast as possible because a plucked sound starts out with a very "sharp", loud attack... immediately. There's no "fade-in" on the volume of that attack. You'd set the second stage's volume a lot lower (so the sound softens) and set it's time also very short. The second stage's time determines how quickly the volume goes from the first stage to the second stage. For a plucked instrument, you want the volume to quickly go from that first, very loud "pick pluck" sound, to the softer sound of the vibrating string.

On the other hand, wind instruments have slower attacks, as the musician's breath pressure builds up. So, your EG settings for a wind instrument may not have as high a volume for the first stage. And you'll have a longer time for that first stage. So, the sound will have a slower "fade-in" on the volume. And the second stage's volume maybe won't be so much lower than the first stage's volume. After all, the building wind pressure may cause an initial "peak" in the volume, but it's not nearly as pronounced as with a plucked string. So there won't be as quick, and wide a change in the volume between the first and second stages.

The third stage of the VCA's EG usually determines not only what volume the sound stays at while you hold down the key, but also its time setting usually determines whether the sound stays indefinitely at that volume (until you release the key -- ie, whether the sound "sustains" indefinitely) or changes to the fourth (ie, last) stage's volume. So, for instruments that can be sustained indefinitely, such as an organ, or a bowed instrument, or a wind instrument (ie, can sustain for as long as the human can continue breathing), then you want to set the EG so it produces indefinite sustain. For instruments whose sound gradually fades out, for example, plucked instruments such as guitar, or piano, or most percussion, you'd make sure that indefinite sustain is turned off, and the last stage's time is set to produce a slow fade-out of the volume.

Applying keyboard tracking to the VCA's Level allows you to have the sound get louder when you play more forcefully, or softer when you play less forcefully. This can be very important for mimicking the characteristics of instruments since the volume of many instruments varies the "harder" or "softer" you play it.


Conclusion

Needless to say, there's a lot more to talk about in creating "patches". You really need to know something about how various types of instruments produce sound, and what that means in terms of overtones, volumes, and other acoustical considerations. There are some books on acoustics and musical instruments that can come in very handy when doing "synth programming". It's perhaps one of the more technically challenging tasks that a musician can do.

One suggestion: You may want to study the VCA and VCF settings in various preset (ie, factory) patches in your MIDI module to see how those settings have been used to contour the sound. Listen to the raw waveform used, and then listen to the preset patch that uses it. Note the change in timbre and volume, and then study the VCA, VCF, and other settings. You should be able to draw some important conclusions about how those settings contour the sound.