Caustic Song file (optional):
Hopefully this type of example bridges the gap between text and video. It will be good to get feedback as to how well this translates the intended info.
And unlike a video it can also be very personally interactive. If you play the file in Song mode there is a gap between each example to give you time to switch between synths and visibly follow along. In Pattern mode you can play around and dissect all you like.
What is sound; what is it we hear?
There is a source and then there are modulators, things that have an effect on the source. Filters, effects like chorus/ flangers / delay, reverb, bitcrushers, eq ... these are all modulators of some sort.
A rifle might be the source of sound. However, before we actually hear the sound it is modulated. It is modulated in many ways such as hundreds or thousands (or more) of subtle echoes (reflections) from walls or trees, rocks etc. It is modulated by air itself and the amount of moisture in the air which affects how frequencies are dampened.
Amplitude is Volume. Modulation is to cause change. So, Amplitude Modulation, AM for short, is quite simply changing the volume.
A very simple form of AM is Tremolo. Many musicians are familiar with Tremolo pedals and effects. Tremolo, along with reverb, was one of the first effects to be built into amplifiers years ago as it only required a simple analog circuit.
Vibrato, often confused with Tremolo, differs in that it modulates the *frequency* (or "pitch") of sound so it is a form of
Frequency Modulation or FM.
In the Caustic file synth 1 is a fairly simple setup. There is a Source, the waveform generator (often referred to as as oscillator) which is modulated by an envelope.
Synth 2 is identical in sound, the only difference in the setup is that the sound is first sent into a mixer. By attaching the DADSR envelope to the Mod input of the mixer instead of the waveform generator it clearly demonstrates that the Mod input jacks function identically. Make sense?
This is cool because now this setup allows TWO different ways to modulate amplitude. (3 for the more advanced readers as the Volume Mod input visible in the upper right corner exists but let's not cloud the issue for now).
On to synth 3. The DADSR is again attached to the waveform generator allowing control of tne initial sound. We can control the attack, decay etc. For example if you press a key the volume still swells in and slowly releases. However, there is now a MiniLFO attached to the mixer Mod.
The MiniLFO is quite simply a waveform generator, nothing more. However the frequency coming from it is so slow it doesn't even produce sound in the range of human hearing.
The sine wave coming from the MiniLFO is Modulating the amplitude whenever the DADSR envelope is allowing sound to pass into the mixer, in other words when you play a note.
This creates a distinct Tremolo effect. The MiniLFO is helping out as it automatically raises and lowers the volume as long as the note sounds.
You'll notice the rate of the MiniLFO is automated. As the speed of the amplitude modulation increases, when the MiniLFO reaches a high enough frequency, it starts to produce a "sympathetic"note. The sympathetic note first added to the sound is actually a lower pitch than the original produced by the waveform generator.
If we want higher pitched notes we need an oscillator that will run a little bit faster than the MiniLFO. That's where the Sub Oscillator comes in. At the lower octave settings the Sub Osc produces roughly the same speed of modulation as the MiniLFO at it's highest rate.
In synth 4 the MiniLFO has been replaced by the Sub Osc. When you play the file the initial sound is a similiar pitch to where the MiniLFO finished. Now we can listen to what happens as we increase the amplitude modulation even more.
Eventually we reach the maximum speed limit (frequency limit) of the Sub Osc just as we did with the MiniLFO, so, now we need ANOTHER way to Modulate the amplitude at a faster frequency.
That's pretty easy - now we use a standard waveform generator as visible in synths 5 and 6.
So, there are 3 principal ways to generate a sine wave in the Modsynth so far:
1 - MiniLFO (frequencies generally too low for human hearing)
2 - Sub Oscillator (frequencies at the lowest range of human hearing, similiar to low end rumble like earthquakes, passing trucks, explosions etc. We feel these freq as much of more than we actually hear them).
3 - Waveform Generator (frequencies that generally cover the full range of human hearing)
You can Modulate the amplitude using other waveforms like a square wave. Notice that with synth 7 that, unlike the smooth volume changes that occur with a sine wave, the sound is either on or off.
Using different waveforms to Modulate the amplitude gives different results so understanding that helps determine choices.
The other examples are a little more difficult to understand but essentially with the alarm sounds the amplitude is still being modulated, whether it is two sounds at the same time (alarm 1 with a mixer), at the opposite time (alarm 2 with a crossfader) or being panned between two sides (the following alarms).
The Crossfade module replaces the mixer in some of the alarm examples, as does the Pan module. This allows Modulating two different sources at once. If the mixer were used, both sounds would turn on or off at the same time. With the crossfader you can modulate between different sources. With the Pan module you can modulaye from side to side. Using both to Pan alternate between the two sounds and simultaneously Pan them.
Notice the MiniLFO allows controlling the mixer, panner and crossfader at the same time.
The sudden change in amplitude caused by the square wave can sometimes result in clicking. In the final example a lag processor is used. It slightly smooths the abrupt change in volume. It is not even audible as it happens so quickly but it slows the attack of each modulation just enough to eliminate the clicking.
And finally, the output of the MiniLFO used in the final alarm is automated. When it is turned off (output is zero) the waveforms are no longer modulated by the LFO... the amplitude does not change and the two source sounds no longer pan.
Hopefully amplitude, mudulayion and the modular synth are now slightly less confusing or intimidating than before.