Electronic Music Interactive, 2nd edition

2. Sound as a Representation

In traditional music, a musician touches and manipulates and works directly with an instrument to create a desired sound. This takes different forms on different instruments. The pianist depresses keys on a piano, the violinist draws a bow across a string, a percussionist strikes the head of a drum, and so on. In each of these cases the musician interacts directly with a vibrating sound source.

Representing Traditional music with a volin's sounds going to a ear.

Diagram 2-1: Traditional Music.

In electronic music, however, the loudspeaker is the ultimate vibrating sound source. To create music, electronic musicians do not strike or bow the loudspeaker to produce sound. Instead, electronic musicians must work with representations of sound. This process of manipulating and shaping "representations of sound" is the essence of electronic music.

Representing sound captured then played through a speaker to the ear.

Diagram 2-2: Electronic Music.

Sound can be "captured" or converted into a representation. A microphone converts waves of acoustic energy (sound) into electrical energy in the form of fluctuating voltage. This electrical energy contains fluctuations in voltage analogous to the fluctuations in air pressure made by a sound. This "captured" sound is called an analog representation and the electrical version of the sound is an analog signal.

Example 2-3: A microphone changing acoustic energy to fluctuating electrical energy produces an analog signal.

Once sound is represented by an analog signal it can be processed or stored in several ways. It may be amplified (strengthened in power) and sent to loudspeakers that are electroacoustic transducers (or transducers) converting the analog signal back into acoustic energy.

Analog Signal going into a amplifier then being produced as Acoustic Energy(sound)

Diagram 2-4: Analog conversion.

An analog signal may also be sent to a tape recorder where it is imprinted as a magnetic representation and stored as a recording. This analog recording is a result of the conversion of the fluctuating voltage found in the analog signal. This process can be reversed by playing the tape, which converts the magnetic record back into an analog signal.

Series of images, going from a sound source (violin) to a microphone, show the fluctuating voltage as a tape recorder records the sound, then is played through a speaker.

RECORDING

Example 2-5: An analog signal may be stored on tape as an analog recording.

Finally an analog signal may be routed to a device called an analog to digital converter (also called an A/D converter, or ADC). This device changes the analog signal into a series of discrete numbers which represents the voltage fluctuations in the analog signal. This "digital representation" is discussed more extensively in the topic "Digital Representation of Sound".

Once in digital form the signal may then be shaped and modified using digital tools. It may also be sent to tape or disk where it is encoded and stored as a digital recording. This type of recording is called a digital recording because the sound is stored as a series of discrete numbers.

The digital version can be converted back into an analog signal with a device called a digital to analog converter (also known as a D/A converter, or DAC). The digital to analog converter changes the digital information (the numbers) back to an analog signal. This analog signal can then be sent to an amplifier, and subsequently to speakers where it is changed to acoustic energy, producing sound.

A process of showing the conversion from analog sound to a digital recorder then converts it digital noise then back into analog for a speaker to play the sound.

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Example 2-6: The analog signal may be sent to an analog to digital converter (A/D converter, or ADC), converted into a digital signal, and stored as a digital recording.