17
Finally, you should experiment with the control of the CLOCK
itself by SEQ 2. This is accomplished, as the panel indicates,
by pulling the clock frequency control knob out from the panel
about a quarter-inch. Do that; notice that the stepping rate
suddenly becomes irregular, but forms repeating patterns every
eight steps. Now the length of any one step will be determined
by the SEQ 2 CONTROL VOLTAGE PRESET for that step. Use the pre-
sets to set up a regular rhythm; the clock frequency control
will determine the overall tempo.
NOTE: Since, when the SEQUENCER TRANSPOSE switch is at the SEQ
2 BY CV 2 position, the keyboard second control voltage is
added to the voltage output of SEQ 2, then when the CLOCK fre-
quency is being controlled by SEQ 2, the frequency will also be
determined by the keyboard. IN OTHER WORDS, this setting gives
you keyboard control of a sequencer tempo!
G. THE SAMPLE AND HOLD UNIT
The control voltages produced by SEQ 1 and SEQ 2 are programmed
at each step by the performer. Voltages from the SAMPLE/HOLD
unit are random. Listen to voice one under control of the s/h;
begin with the two knobs in the s/h section rotated maximum
counterclockvise, and slowly increase the range setting. The
first voice produces a series of random pitches over a wider
and wider range as the knob is rotated further to the right.
The lag knob introduces a portamento into the pitch
changes--longer as it is rotated to the right. Try it.
The middle position of the VCF control selector, labelled
"EXT", carries a 9/h voltage to control the filter. Try using a
noise input to the filter, open only to about two o'clock, and
set the filter to bandpass operation at maximum resonance. Use
a short percussive envelope on the VCA and adjust the VCF fre-
quency to about the middle of its range or a little higher.
Open the control input attenuator on the filter while the s/h
is running. You should hear a series of percussive events of
various noise colors. Remember doing this by hand back at page
twelve?
You can introduce accents into the series by lengthening the
decay time on the VCA envelope: try it. Make the patch more
complex by setting up the keyboard-control-of-tempo effect you
learned in the preceding section.
H. PERFORMING HINTS
You have now learned something about each of the functions in
the Oberheim 2-voice synthesizer, and something of how each
