Sound – The Voltage Controlled Oscillator or VCO
Before we can hear anything, we would need a tone generator. A tone is basically an oscillating (vibrating) waveform. There are three distinct categories:
Well known examples are the sine, saw and block waves. Bob Moog made them famous and there’s nothing like the Moog sound on a bit of reverb.
Obvious examples from the synth world are the pink- and white noise. Less obvious examples are the shapes of a wavetable synth, the sound of a violin or sax and the human voice. Recorded music is a complex waveform too.
Frequency Modulated (FM) Waveforms
Many complex waveforms are the result of adding two or more waveforms together so a new sound is created.
OK, we have an oscillator that does BZZZ all the time. This is becoming very boring quickly, so we need to feed it a note to play. And voltage is the way to do it, basically with 1 volt per octave. So we can control the note by changing the voltage. This can be done smoothly (by turning the knob). It can be done by giving it a specific control voltage (CV) that matches a specific key. So a CV connection on a VCO will let you control its pitch. Sometimes this CV connection is labelled V/Oct which is the common norm so you have nothing to worry about. There’s also a V/Hz system created by the famous mr. Donald Buchla who pioneered the synthesis world half a century ago. So you could need a ‘converter’ if you happen to own a vintage Buchla and want to hook it up.
Vintage synths use the subtractive technique: you start with a simple waveform and then you start ‘cutting away’ the sounds you don’t like. This is done by filters and envelopes. Great examples of these synths are the Moog and the Jupiter 8.
Additive synths take the same simple waveform, but they add a second waveform to let mother nature make a new sound (FM). In Western music, instruments are tuned at 440 Hz (A4). You can make it drop an octave by subtracting half of it. You can rise an octave by multiplying it by 2. Regular synths allow you to do that by turning the frequency knob. With FM synthesis, you can add a second waveform that will transform the original into a new one. So if you ‘add’ a 440 Hz (A4) to itself, you’ll double the frequency to 880 Hz (A5). Yes, doubling the frequencies takes you an octave higher. If you want to go down an octave, you’ll need to divide it. This also shows the relationship between nice sounds that fit the harmonic scale of a piano keyboard. Metallic and percussive sounds don’t have a clear note. You’ll get these sounds by experimenting with values out of that scale. Some legendary additive / FM synths are the Yamaha DX7 and the Synclavier.
And then there’s sampling. Personally I love sampling, because in theory, you could use any waveform and blend/mix/modulate it into something else. In the early days when we where still 16 bit and had 65535 values to code a simple waveform (the real time analog version has theoretically endless values) you could hear the difference between a smooth VCO and its jagged cold digital counterpart. But now we are 32 bit with plenty of values (billions) to emulate the moog sine. So sampling has become really powerful and your analog modular may not be completely analog anymore.
However, there will always be a difference in sound when you make analog sounds interact. You can have unpredictable side effects with full analog gear. In the digital domain this is called a ‘bug’ and they usually crash your module. However, the output of a digital module is analog voltage, so you still have all the benefits of an analog modular sound. The most obvious one is: it sounds better and the obvious reason is: it is 10 times louder. You still have to bring it back to the silence of digital, but your source material has incredible dynamic range that will blow out your eardrums.
The best starting point for your quest is Google and ModularGrid. Just search for ‘best VCO’ and you’ll get some really good suggestions from the experts. If you go modular, you’ll probably want FM synthesis and Wave Folding sooner or later, but it may be a good idea to start with simple waveforms first.
A really clever VCO is the Mutable Instruments Plaits (pronounced as Plats) which can give you a vast array of sounds and noise. And FM. And Wave folding. Even physical modelling. It even has a built in triggered VCA for plucky and percussive sounds and a VCA to control its envelope. Really affordable too. Plaits is a must have module in your starter kit.
I’ve been experimenting with lots of case configurations and noticed that the VCO will ultimately define what your case can do. A typical case will have one (powerful, dual) VCO and lots of utilities. The excellent Make Noise Shared System will always sound a bit like a DPO. A full Mutable Instruments case will always sound a bit like Plaits (even when using Elements or Rings with it).