OPERA &
CoTitrot^
the 'T i pit'ch of «s-»[:;oT^fi of^<; i
t
or
wi'th
+0
ih(5
first Ot\e for d f
r«-ii»^*Ticy
i
nt<r?rv^
L of about
hid
if
S* RELATION I^TUEEH WAVE FORHS AND SOUNDS
Th» sh1«c+
i
o»T
of
sound
waves provides set-up of
the syntb
b^slc timbre
for ihfc?
creation of
differeni
groups
of
i
nstr
uinents » For exampL^^^
th^ s«iw--tt>oth
wave < ) which
contains odd and ev«.?n harcnanics will, be useful tu venerate
strings end
brass instruments sonorities*
The sitiere
wave
i > With a P4U+ at about SOK w < I. V lje
useful
to
create timbres such as the r lari net;
as
soon as the
S4.uars
wave becomes asymmetr i c
*
operating the P^U* knob it*A content
will change and become move complexi as a lesult you will
obtain a "nasal" soundi- suited to the imitation
of reed
instruments such
as
the
oboe# the
bassoon#
e?tc 4 Thfc^ audible
differences
from wave
to
wave
depend on their different
harm
on
i c
c
o
otents
*
A complex sound (s<Luare wave#
s^^iuare
wave with different
P*W*f
saw-tooth wave#
etc*> is
the
total of pure rounds Csine
waves) in which the basic note (note whicl^
determines
the
pitch) has a single amplitude and all the nthers#ca
t
led
harmonic notes# have a different
ampliti^ide
depending
on the
harmonic; spectrum of the complex wave analysed*
The graphics hereu ruder <Ahow
the
harmonic
*ipectrum of the
OPERA 6 ^vund waves with respect to the 100 Hst basic
fre'iiiency*
6* U*C+F* (UoLtage Controlled Filter)
A.i cuTorr
This knob adjusts cutoff fre^tuency of the
24dB
octave
<4
pole) Low-Pass filter* It is rather
like
a lone
control*
^*Cutoff^' ts
the frequency below
which
all
elements
of the
mixer's output signal are Let through* Tlie h i gher—tr e*iuency
components of
the
input
signal ( i +e* all those above the
cutoff fresLuency) are suppressed
+ The liigher the
knob
setting# the higher the knob f re^uenc i
are
which pass
through the filter* Tl^us#
the
l^igh&r
the
sound* The diagrams
hereunder
sJiow the progressive suppression
of the high
fr»iuencies of a saw—tooth wave according to the
lower
and
lower filter cutoff*
A.
Unf
titered saw-tooth wave
StFreiuency cutoff set-off
C*
Cutoff frequency suppY^ession D*Formati&n
of
an almost
sine wave with
cutoff
tuned on the
same fre-
*iuency as the
basic note*
E* Fret^uency
cutoff
^t to 0* no sound output
\
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