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Introduction 2. Theory of the Synthesizer 4 4 1 A synthesizer is not an organ. The basic difference lies in the synthesizer’s ability to freely modify sound envelopes, or, in other words, radically alter the quality of musical sounds. The synthesizer can modify sound envelope elements to change envelope characteristics and thus modify volume and tone to synthesize many sounds which are unlike any which can be produced by conventional instruments, in addition to sounds which are exactly like those of conventional instruments. Thus, the Synthesizer has the inherent capability of extending the range of musical conception through production of unique new sounds. The Voice Generator, which generates electronic signals that play an important role in all electronic musical instruments, is composed of the VCO “Voltage Controlled Oscillator”, and its musical interval is controlled by the voltage coming from the keyboard switch. As the wave form of the music sound produced by the VCO has many harmonics, the desired tone is produced through a VCF or “Voltage Controlled Filter”. The function of the Filter is also dependent on the voltage. The signal through the VCF is modified with regard to the rising, falling or the maintaining of sound by the function of the VCA “Voltage Controlled Amplifier”. Consequently, the VCO, VCF and VCA are the crux of Synthesizer operation. There are included various kinds of voltage generators to modify these three circuits. For example, the LFO (Low Frequency Oscillator) generates an electronic oscillation lower than audio-frequency and supplies voltage to the VCO for Vibrato, to the VCF for Growl, and to the VCA for Tremolo functions. And a SAMPLER incorporating a different LFO taps at regular intervals the input voltage produced by the first mentioned LFO or random voltage produced by the Noise Generator and supplies this voltage into the VCO to create special sounds regardless of individual keyboard notes. 3 The Envelope, comprises elements Attack (A), Decay(D), Sustain(S) and Release(R), as shown in Figure 1 in general form, can be varied according to operation control. Two basic kinds of envelopes can be produced, namely AR and ADSR. The ADSR and AR are also called Envelope Generators. Fig. 2 shows the mutual relation among VCO, VCF, VCA, LFO, SAMPLER, and ADSR. This is the general theory of Synthesizer operation. Of course, besides the abovementioned, there is other function — namely, white-noise generator. Synthesizing these functions in many ways creates even more complicated and more unique sounds. Fig-1 Attack Sustain Fig. 2 V oltage Key OFF ■4 3. Function of the SH-3 a) Keyboard The keyboard employs F scale, 44 keys and 31/2 octaves. It is possible, however, to raise or lower notes by one octave via the Transpose changeover switch to actually extend the keyboard function to 68 keys (91/2 octaves are possible by adjusting the VCO). Due to the employed “low-tone-take-precedence” system, when two or more keys are depressed simultaneously, the lowest tone only is produced. When a key is depressed, a voltage which identifies the tone of the key is supplied to the VCO and at the same time, another fixed voltage is supplied to the ADSR to form an envelope. VCO b) VCO (Voltage Controlled Oscillator) The VCO of the SH-3 comprises volume knobs and change-over switches as shown in Fig. 3. HJ Symmetric Rectangular Wave . . . Contains odd harmonics (3, 5, 7, 9 . . .) to produce.clarinet-like sounds, n—I Unsymmetrical Rectangular Wave Contains many high-tone harmonics. A_ Pulse Wave . . . Contains many high-tone harmonics to produce string sounds like a violin. Each foot-volume knob (32' to 2') is equipped with an output-wave-form selector to produce compound wave forms without limitation. Turning the 8' CHORUS dial clockwise quickens the beat of chorus. VCF o VIBRATO By shifting the VIBRATO knob, depth is changed and normal vibrato can be modulated by the (