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Like to begin synth programming?
28/5/08 12:58:57 AM

As always, hands on will give you a certain level of understanding that books cannot. Synths are made to be played with!

NOTE: What follows is a discussion of 'subtractive' synthesis. It is but one of a few different main types

The Basics:

An oscillator refers to some unit within a synthesiser that may produce a uniform fluctuation in an audio signal over time. I say 'unit' because in an analogue synth, this is an analogue electric circuit (probably on a chip, but not digital). Modeling synths will have a very short digital sample of the waveform shape stored in some kind of ROM. For all intents and purposes, the outcome is the same.
Oscillators can have different shapes, meaning what their level output would look like if plotted on a graph over time. The 'shape' is a very important selection to make when you are beginning a new sound on your synth. It determines the harmonic possibilities available. Harmonics are 'overtones' related to the fundamental tone or rate of oscillations per second. They give character and tonal signature to the sounds of things. Different waveform shapes offer different harmonic overtone content.

Something to note here is the range of frequencies which humans may reasonably hear. A frequency is nothing more than the rate of occurrence over a given time frame. The measurement of 'Hertz' is for how many times something occurs within one second. A clock ticks at a rate of one Hertz. A metronome with a setting of 120 beats per minute will be operating at 2 Hertz.
Humans don't perceive something to be an actual audible tone until that thing occurs at least 20 times per second, or has a frequency of 20 Hertz. If you could set your metronome to tick at a rate of 20 Hertz, you may hear a very low tone or note.
At the other end of a humans range of hearing are oscillations of 20,000 Hertz. You need a pretty good set of ears to hear a pitch this high though! And there's an interesting word, 'pitch'. Pitch is nothing more than the frequency of a tone. The frequency of an open 'A' string of a guitar tuned to concert pitch will be 440Hz (Hz = Hertz).

Low Frequency Oscillators
Most commonly referred to by their acronym, LFO, these devices are used to 'modulate' the audible signals or the operation of signal effectors (more on these following!).

Modulation simply means to change something over time.

Think of an LFO as nothing more than a very low frequency oscillator, whos cycle takes place over seconds, rather than multiple times within a second. This is not a rule however, as most LFOs may have their rate set up into the audible range (above 20Hz).
You don't hear an LFO though, regardless of it's frequency. That's because it's output is not (usually) connected to the audio path of the synth. It's output is connected to 'something else'.

Like what???

An LFO is good for making something change constantly. A slow cycling LFO controlling the frequency of an audio path oscillators (one designed to output a tonal signal like the ones I discussed first up) frequency can make a siren effect. The 'level' of the LFO can be used to control the value of nearly anything in the synth!
In the siren example, the LFOs output is constantly rising and falling over a cycle, over a certain time. This rising and falling will create a wave shape on a graph, identical to the above mentioned audio oscillators, but because we connected the LFOs output to control the frequency of another oscillator, we get a rising and falling in pitch.
You can change the shape of the LFO too! The siren effect would require a triangle or sine wave shape. Try and imagine what effect a square or sawtooth wave would have on the output?

The speed (frequency) and depth (amplitude (the height of the wave)) of the LFO can be set as required, but it does not only have to be controlling the pitch of another oscillator. There will be MANY settings able to be controlled by an LFO on your synth! Check them out under something like 'LFO destinations' or 'LFO routings'. See what happens when you control different things with an LFO of varying frequencies and depths.

In addition to modulating things with LFOs, you can also use envelopes. An envelope is like a one shot LFO, where you have control over the actual wave shape. An envelope responds to a trigger and that'll usually be you playing a note. Once you trigger an envelope, your settings control the effect of the envelopes modulation over a certain timeframe.
This is the first setting on 99% of envelope generators. It controls how quickly the volume of your note will rise from zero to full level. The lower the ATTACK setting, the quicker your note will hit full volume. A high ATTACK value will cause the notes volume to rise slowly.

DECAY is a little weird to understand at first, so let's skip to the next usual parameter, SUSTAIN!

This is a volume setting that will be used for as long as you hold down a note. Quite often it is set to be lower in volume level than the maximum volume. DECAY is a setting for the amount of time it takes the volume to get from it's maximum level, to the volume level set by SUSTAIN.

Simple! This is how long the note will ring from the point where you release the key.

Now just as LFOs can modulate MANY different synth parameters, so too can envelopes. Read on, and I'll explain in more detail.

You will probably come across two main types of filters. LOW PASS and HIGH PASS. A LOW PASS filter simply prevents frequencies above a certain setting to pass it. It's name makes sense when you think about it! It's like a maximum height sign for a bridge. If your truck is too high, the top will be cut off. In this case, high frequencies are cut off. And that's the name of one of the LOW PASS filters controls, 'cutoff'. Adjusting this dial will set the point at which frequencies begin to be 'removed' or blocked from the output of the filter. It's important to remember that most sounds coming out of your synth will consist of a fundamental frequency (the actual note you can perceive) and then a series of related higher frequencies (harmonics) that all sound together as one note. The filter removes these higher frequencies and thus, removes their effect on the tone of the sound.
The other usual control to be found on a filter is the RESONANCE dial. This control adjusts how much of the actual frequency at the 'cutoff' point gets sent back into the filter! Sounds weird right? And it does!
This lends a certain brilliance to the effect of the filter and can lead to squelchy and wet sounds. :-)

The other main type of filter that you'll come across is the HIGH PASS. I won't say anymore other than the HIGH PASS filter is the opposite to the LOW PASS filter!

To sum up the basics, imagine what would happen if you applied the modulation devices to the filter cutoff setting? An LFO will create automatic filter 'sweeping', just as though you were holding the 'cutoff' dial and manually sweeping it.

The envelope would do the same, but it would only happen at each key press. This would be like an 'auto-wah' effect. :-)

Anyways, that is only the VERY basic scratched surface of what a subtractive synthesiser can do! I plan on making some videos that will explain all this in a much clearer way, but I hope this helped you a little bit.

And here are some things you can try out:
o Start with a blank canvas, so to speak, and then turn only one oscillator on.

o Cycle through some oscillator waveform shapes and hear what tonal qualities each has. Try to stick to the 'classic' waveform shapes like the sawtooth, pulse wave and triangle. Your synth may have many more, but these waveform shapes will be all you'll need for creating classic analogue sounds.

o Change the tuning range of this oscillator and hear the affect this produces.

"Words are the rails upon which the train of thought runs."

23/7/08 10:19:42 AM



This guide will be pretty useful when this gets released (I cannae afford the real deal, but this looks like it'll serve as a useful little simulator!)

It's curtains for you, Doctor Horrible. Lacy, gently wafting curtains...

23/7/08 10:31:23 AM

There are plenty of free software synths for PC/Mac out there. You can't take them on the bus as easily, but they would be just as good, if not better to learn on.

I can teach you to play guitar for FREE!

23/7/08 11:19:07 AM


I like synth...but never used one.

They sound brilliant, but I don't know if I've the time or indeed the ability to make enough of an effort to learn to use one.

Might scope out these software versions, you've mentioned and have a play.

It's curtains for you, Doctor Horrible. Lacy, gently wafting curtains...

23/7/08 12:27:11 PM

Synth programming is nothing more than knowing what the modules do. The rest is just playing around until you get the sound you want. This goes for both subtractive (what you are looking at) and FM (frequency modulation, as used by the Yamaha DX7).

Very simple really, but the possible variations are huge.

I can teach you to play guitar for FREE!

24/7/08 3:37:44 PM

Thanks...I liked to muck around with them, but I could never understand (or be bothered with jargon) to figure out what the terms meant or how they worked. Nice article!

I no longer want to be a man. I want to be a horse. Men have small thoughts. I need a tail. Give me a tail. Tell me a tale.

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