A Brief History
As mentioned in Introduction II, John Chowning brought a copy of the MUSIC IV software
from Bell Labs to Stanford, where he founded the CCRMA,
and started experiments in sound synthesis.
Although frequency modulation was already a method used in
analog sound synthesis, it was Chowning who developed the concept of frequency modulation (FM) synthesis with digital means in the late 1960s.
The concept of frequency modulation, already used for
transmitting radio signals, was transferred to the
audible domain by John Chowning, since he saw the
potential to create complex (as in rich) timbres
with a few operations (Chowning, 1973).
For one sinusoid modulating the frequency of a second,
frequency modulation can be written as:
\[ y(t) = \sin(2 \pi f_c + I_m \sin(2 \pi f_m t) ) \]
\(f_c\) denotes the so called carrier frequency,
\(f_m\) the modulation frequency and \(I_m\)
the modulation index.
[Fig.1] shows a flow chart for this operation
in the style of MUSIC IV.
- Fig.1
-
Flow chart for FM with two operators (Chowning, 1973).
In many musical applications, the use of dynamic spectra is
desirable. The parameters of the above shown FM algorithm
are therefor controlled with temporal envelopes,
as shown in [Fig.2].
Especially the change of the modulation index over time
is important, since it results in percussive sound qualities.
In musical applications, multiple carriers and
modulators, referred to as operators,
are connected in different configurations, for
generating richer timbres.
- Fig.2
-
Flow chart for dynamic FM with two operators (Chowning, 1973).
FM synthesis is considered an abstract algorithm.
It does not come with a related analysis approach
to generate desired sounds but they need to be
programmed or designed.
However, there are attempts towards an automatic
parametrization of FM synthesizers (Horner, 2003).
John Chowning, composer by profession, combined the novel
FM synthesis approach with digital spatialization techniques
to create quadraphonic pieces of electronic music
on a completely new level.
In Turenas, completed in 1972, artificial doppler shifts
and direct-to-reverberation techniques
are used to intensify the perceived motion
and distance of panned sounds
in the loudspeaker setup.
The sounds used in this piece are only generated by
means of FM, resulting in a characteristic quality
like the synthetic bell-like sounds beginning at 1:30
or the re-occuring short precussive events.
References
2011
- John Chowning.
Turenas: the realization of a dream.
Proc. of the 17es Journées d’Informatique Musicale, Saint-Etienne, France, 2011.
[details]
[BibTeX▼]
@article{chowning2011turenas,
author = "Chowning, John",
journal = "Proc. of the 17es Journées d’Informatique Musicale, Saint-Etienne, France",
title = "{Turenas: the realization of a dream}",
year = "2011"
}
2003
- Andrew Horner.
Auto-programmable FM and wavetable synthesizers.
Contemporary Music Review, 22(3):21–29, 2003.
[details]
[BibTeX▼]
@article{horner2003auto,
author = "Horner, Andrew",
journal = "Contemporary Music Review",
number = "3",
pages = "21–29",
publisher = "Taylor \\& Francis",
title = "{Auto-programmable FM and wavetable synthesizers}",
volume = "22",
year = "2003"
}
1973
- John M Chowning.
The synthesis of complex audio spectra by means of frequency modulation.
Journal of the audio engineering society, 21(7):526–534, 1973.
[details]
[BibTeX▼]
@article{chowning1973thesynthesis,
author = "Chowning, John M",
journal = "Journal of the audio engineering society",
number = "7",
pages = "526–534",
publisher = "Audio Engineering Society",
title = "{The synthesis of complex audio spectra by means of frequency modulation}",
volume = "21",
year = "1973"
}