Chapter 5: Electronic Music and Synthesizers

Who uses electronic musical synthesizers?

Each advance in electronic technology is followed by a concomitant advance in synthesizers and new developments in the expressive range of electronic music.

Chapter Outline:

1. Combination of waves

2. Analog synthesizer

3. Digital synthesizer

Combination of waves and Modulation

Methods of combining waves:

1.Simple addition (Superposition)

2.Gating

3.Amplitude modulation

4.Balanced modulation

5.Frequency modulation

6.Pulse-width modulation

Gating

Amplitude Modulation (AM)

100% Modulation and Overmodulation

Balanced Modulation

Frequency Modulation (FM)

Radio Waves

FM vs AM: What's the difference?

AM: The amplitude of the signal is varied to incorporate the sound information. Frequencies are in kHz.

FM: The frequency of the carrier signal is varied to incorporate the sound information. Frequencies are in MHz.

FM vs AM Advantages and Disadvantages

FM signals are not affected by static.With an FM broadcast, slight changes in amplitude don't matter -- since the audio signal is conveyed through changes in frequency, the FM receiver can just ignore changes in amplitude.

AM carrier waves have much longer wavelengths than FM carrier waves, and as a result, they can bend around obstacles like mountains and buildings better than FM waves and can travel greater distances before the signal fades.

Pulse-width Modulation (PWM)

Analog Synthesizer

Signals

Two types of signals are used in a synthesizer: audio signals and control signals.

Audio signals: electronic signals with frequencies in the audible range and amplitudes of about 1.5 V, which can be input to a speaker.

Control signals, oscillatory or constant in voltage, amplitudes up to about 5 V, used to control the operation of various components in the synthesizer.

KeyboardProvides two functions:

Gives the control signal that determines the pitchProvides the starting signal that triggers the envelope generator.

Sample and Hold

In general, a keyboard pitch-control signal is input to the oscillator, and the audio output from the oscillator is sent to a speaker.

Pressing a key will then cause the production of a tone with the pitch associated with that key.

The oscillator remembers the pitch and continues to sound at this pitch even when the key is released, which is known as Sample and Hold.

The tone will then continue at the same pitch until another key is pressed, at which time the oscillator will remember the new pitch.

Voltage-controlled oscillator (VCO)

Voltage-Controlled Amplifier (VCA)

Envelope Generator

Block diagram with envelope generator