ARP 2600 - Keyboard Tuning and Interval Controls

38
other.
Thus,
under
these
conditions, when the
KBD
CV
controls
any
VCO
in the
2600,
the
VCO
will respond
with
one
audio
octave inter-
val for
every
octave interval
played on the
keyboard;
and intermediate
keyboard Intervals will
produce the standard musical intervals
of
a
tem-
pered
scale.
When,
however,
the slide
switch is
in its left-hand
position,
the
KBD CV
passes through
a rotary attenuator that
may
be user-adjusted
to a
wide range
of
values. With this
knob
turned to its maximum
counterclockwise position, the voltage differences produced
from
one
end
to
the
other of
the
keyboard
is
only
about
one
volt, or
(when
con-
trolling
a VCO) a musical interval of about
one
octave. This
octave
is
therefore divisible
into
as
many
microtones as
there are keys on
the
3604.
When the
TONE INTERVAL knob is turned to its
maximum
clockwise rotation,
the
voltage interval from
bottom
to
top
of the
keyboard
is not
quite eight
volts,
or
(when controlling
a VCO)
a
mus-
ical
range
of
somewhat less
than
eight
octaves.
Thus
the
musical
interval represented
by the
four keyboard
oc-
taves
of
the
3604
may
be
adjusted
over a
wide range
by the
TONE
INTERVAL control.
Normally
the voltage represented
by
the
lowest
note on
the
keyboard
is
zero.
The entire keyboard output
voltage
may
however
be
adjusted
over
a
+.5
V
range from
this
reference
by
use
of the TUNING
control.
When
the switch for this control is
in its right-hand position,
the control
is
disconnected and has no effect
on the output voltage.
When the switch
is in its
left-hand position, the TUNING
knob as it
is
rotated clockwise
will gradually
raise the
KBD
CV
to
about a
half-volt
higher than its corresponding
value
with the TUNING
control
switched
off.
By
means
of
this
control, when
the 2600 is
being used
with other
instruments
it may first be brought into
tune with itself and
then
tuned
to the other
instruments
(provided the
initial tuning
is
within half
an
octave below the intended pitch).
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