ARP2600 - Fundamentals of Music Technology - Cyborgstudio.com

SECTION2 VCO-1ALL ABOUT OSCILLATORSOscillators are the fundamental part of any synthesizer. They are the module that creates the raw soundthat will be shaped and molded by all the other parts of the synthesizer. Oscillators function by puttingout voltage in a pattern. The faster they put out the pattern, the higher the frequency they produce.When this output voltage is amplified and connected to a speaker, a sound can sometimes be heard.Some people think that oscillators only put out voltage when a key is being played on the keyboard.This really isn’t true, though. Oscillators constantly oscillate at a specified rate, even if a key isn’t beingplayed. Another word for rate is frequency and it is measured in Hertz (Hz).+10Volts0timeFigure 2-1: A square waveVCO stands for voltage controlled oscillator. This means thatthis module is an oscillator and can produce audio signals andcontrol signals. It also means that at least one of its parameterscan be controlled via voltage control. This is another perfectexample of the term ‘voltage controlled’ being used as an adjectiveas mentioned in Section 1.Most oscillators are capable of producing different tone colors. This is accomplished by putting outvoltage in a pattern called a waveform. For instance, to create a square wave (see Figure 2-1), theoscillator will put out no voltage for a moment, then put out ten volts for a moment. To produce a sawwave (see Figure 2-2), the oscillator must increase its voltage gradually to ten volts, then drop sharplyback to zero volts.Repeating a waveform very quickly (often thousands of timesper second) produces an electronic signal which human earswill perceive as a tone after it is amplified and is connected toa speaker. Notice when the raw output of an oscillator is connectedto a speaker that the sound is not particularly interestingto listen to. Because the sound is static and unchanging, it israther monotonous or boring.10volts0timeFigure 2-2: A saw waveTHE OSCILLATOR’S TIMBREOscillators have two different parameters, the first of which is timbre. Timbre comes from French, andis pronounced tam-ber. Timbre means tone color or raw sound. When timbre changes, the shape of thewaveform changes. One can easily see by comparing Figures 2-1 and 2-2 above that a square wavedoes not look anything like a saw wave. The two will sound different as well, just the way a pianosounds different from a trumpet, even if each sounds the same note.One selects a timbre by connecting a patch cord to one of the oscillator’s two outputs. In Figure 2-3,VCO-1’s two outputs jacks can be seen. The top jack constantly puts out a saw wave and the bottomjack puts out a square wave. It is very important to note that connecting a patch cord to one of the two011