Synthesizers

A term paper about the basics of music synthesis.

Modern synthesizers are able to produce sounds identical to those of real instruments using computers. Synthesizers produce sound by electronically imitating sound waves; more advanced sounds are produced by manipulations of these basic sound waves. Synthesizers are used frequently in modern music.

The fundamentals underlying sound synthesis are based in acoustics, the science of sound. Sound is a wave produced by vibrating objects that transfer this wave to the air around them; sound is most frequently represented as a wave known as a waveform that shows the changes in air pressure over time (Rothstein). Objects that produce recognizable pitches vibrate predominantly on a single plane; vibrations on many planes produce interference between vibrations that results in noise without a pitch (“Sound”). Synthesizers imitate the natural vibration of objects with electrical waveforms that are identical to the sound the synthesizer is attempting to produce. The resulting vibrations are made audible by increasing the amplitude of the sine wave (Rothstein). Synthesizers that only produce individual tones have simple waveforms identical to sine curves; synthesizers that are more complex have more complex waveforms reflecting the multiple frequencies of the sounds they produce (“Sound”) The complex waveform of sounds with multiple frequencies is a graph of the results of interference between the waveforms of the frequencies (“Sound”).

Most sounds are combinations of a fundamental tone and multiple overtones; each instrument has a unique set of overtones that gives it its timbre, or unique sound “color”, which allows for distinction between different instruments (Rothstein). In sounds with no distinct musical pitch, such as the crash of a cymbal, these overtones are generally unrelated to the fundamental tone (“Sound”). In “musical” sounds, these overtones are integral multiples of the fundamental tone; the first overtone is twice the fundamental, the second is three times the fundamental, and so on (United). The relationship between overtones is logarithmic, meaning that the difference in frequency between overtones increases with the overtones (Rothstein). Synthesizers often do not sound like the instrument they are designed to because while they easily produce the fundamental tone, they do not accurately reproduce the overtones of that instrument. Simple synthesizers produce only the fundamental tone, giving a recognizable synthesized sound; more advanced synthesizers utilize overtones as well, allowing for a greater range of musical sounds.

One common method of synthesis involving multiple frequencies is additive synthesis, in which overtones are added over the fundamental tone, creating a complex waveform similar to actual musical instruments from a sinusoidal waveform (“Sound”). Another common method, subtractive synthesis, is the opposite of additive synthesis, in which sounds are filtered from a wide array of sounds to produce the desired fundamental and overtones; the waveform in this type of synthesis transitions from incredibly complex to less complex (“Sound”). Another digital music method often perceived as synthesis is sampling, in which the waveforms of acoustic samples of sound are digitally altered; as the sounds are not artificially produced, however, it is not true synthesis (Rothstein). Many recently developed synthesizers attempt to produce waveforms of sound by emulating how the sound is naturally produced; these synthesizers create complex representations of real objects digitally and use the resulting data to produce a waveform (“Sound”).

Digital synthesis is based on the scientific principles of sound. Synthesizers emulate acoustically produced sound by producing electrical signals with identical waveforms. Advanced synthesizing methods involving overtones enable the digital production of a wide range of musical sounds. The versatility of synthesizers enables their widespread use in modern music.

Sources:

Rothstein, Joseph. MIDI: A comprehensive introduction. Madison, WI: A-R Editions, 1995.

“Sound synthesis tutorial”. University of Salford. 28 Apr 2010. .

“Synthesizers”. Wikipedia, the free encyclopedia. 29 Apr 2010. .

United States. General Services Administration. "Overtone." Federal Standard 1037c.  Institute for Telecommunication Sciences, n.d. Web. 2 May 2010.  fs-1037c.htm>.