9
2. TWO BASIC IDEAS ARE INVOLVED in a!! electronic music
synthesizers.
2.1 THE FIRST is that ACOUSTICAL WAVEFORMS CAN BE GEN-
ERATED AND MODIFIED PURELY BY ELECTRONIC MEANS.
2.1 1Banging on agarbage can lid generates ahorrible racket by
mechanical means. The racket is avery complicated sound; but no mat
ter how complicated it gets, it can be reproduced by asingle long and
complicated wiggle in aphonograph record. So can asymphony. From
acertain point of view all the sounds you've ever heard, ever will hear,
and ever could imagine, must be reducible to one (or at most two—one
for each ear) complicated wiggle of your eardrums.
2.1 11Edison's phonograph recorded by mechanical means the vibra-
tions he fed into it. The cylinder— and later the disc—stored them as
mechanical wiggles in agroove; on playback, running this groove past
aneedle made the needle wiggle, the needle made adiaphragm vibrate,
and the diaphragm passed it on to the air in the form of pressure vibra-
tions, and the air transmitted the sound waves to somebody's ears.
2.1
1
2Nobody has done it that way for quite awhile now. Today, a
microphone turns sound waves into electrical signals. In other words,
rapid and periodic fluctuations in air pressure are transformed into
rapid and periodic fluctuations in some electrical phenomenon—usualiy
avoltage. In this form the wave can be electrically amplified, equalized,
filtered, and subjected to various other indignities beforebeing sent to
arecording lathe that turns it back again into amechanical waveform in
agroove. Likewise, when the record is played, the stylus wiggles the way
it did in Edison's player, but its vibrations are immediately turned into
electrical signals. They don't become mechanical again until they reach
the loudspeaker.
2.12 IN ALL THIS, THE ONLY THING THAT DOESN'T CHANGE
IS THE SHAPE OF THE WAVE, i.e. THE WAVEFORM.
2.1 21 Suppose you bang an A-440 tuning fork on the corner of the
table. In 1/440th of asecond, then, the fork makes one complete vibra-
tion back and forth: .*bOL0M+>
vosi&ori cifr reef-
forth
;440-sec
