Lexicon PCM 42 - 4.3 Programming and Using the Metronome;Clock Output; 4.3.1 Setting the Clock Rate

Many performers who have made use of tape looping
bade ceils nsate ed ce this problem by usi ing a slow, ar-
with lon k times, or simply |
looy to the studio. A ow have
aE reload: el laborate means of measuring the pt tim 1e
ina tape loop. All of these strategems have sharp limita-
tions In application. oe problem is the nature of
the splice created by ng SAae te oo Without
rite
elaborate and expensive 2 sp Cl ssing, the instan
taneous transition i t occurs at the splice in
an infinite repeat lo a sharp “tick”
which is repeated on loop
All these proble the PCM
42 by a highly yome/clock
output. THIS CLI TO THE
oe OF THE IN} BUT ATA
SELECTABLE ‘FRAC H. For the
2.4-second loop in Fig. 4.5-m, the clock may be pro-
grammed to provide 4 or & output pulses during the
period of the delay, giving intervals of 0.6 and 0.3
seconds, either of which can be easily followed. The
clock pulses are displayed by an LED on the front panel,
or may be taken from the CLOCK OUTPUT jack on the
rear panel and amplified as an audible metronome. And
since the clock rate is adjustable independently of the
delay time, this output may also be adjusted to a more
rapid pulse rate and used to drive external rhythm units.
THE iNFINITE REPEAT FUNCTION [S SYN-
CHRONIZED TO THE CLOCK PULSES. THE MACHINE
ENTERS OR LEAVES INFINITE REPEAT ONLY ON
THE BEAT OF THE METRONOME, REGARDLESS OF
WHEN THE CONTROL IS ACTIVATED. Synchroniza-
tion between the music and the starting point of the
repeat loop can be achieved by watching or listening to
the clock pulse. Once the clock rate is adjusted prop-
erly, a composition may be begun with the confidence
that the end point of the first repeated loop will occur an
exact number of measures after the opening note.
Furthermore, any splicing glitches that occur at the end
of the loop will fall exactly on the beat, where they are
most effectively masked. For detailed instructions in the
programming and interfacing of the clock output, see
Section 4.3 below.
The two audio contro! jacks on the rear panel (MIX
CONTROL and FB CONTROL) are also very effective
tools for use in looping. Connected to Lexicon foot
pedals by means of a stereo phone plug, these jacks
allow foot control over the level of delayed audio in the
output mix, and the amount of feedback in the loop.
With the MIX CONTROL, the user can set up loops that
are faded in and out at appropriate points in the music;
this can be especially effective if a tight synch to the
metronome/clock is maintained. The FEEDBACK CON-
TROL jack provides a convenient means to clear out the
loop in preparation for new material.
a
4.3 PROGRAMMING AND USING THE
METRONOME/CLOCK OUTPUT
4.3.1 Setting the Clock Rate.
in order to set the rate of the Clock Output, first
locate the SET-MODE s witch on the front panel [Fig.
2.1, K]. When this switch is moved to the CLK position,
the 4-digit display of ecg time ts replaced by a two- or
three-digit display with blank spaces in between. This
display is read as a fraction of the delay memory size.
For ae ee on power-up this display Is set to read
| ould be read as the fracti 1/2" and
35 that ei period of the clock Is see 4G one-half
of the de elay time obtained by advancing to the maximum
value settable by the UP and DOWN pushbuttons.
A br a experiment will make this concept clear. Slide
the SET-MODE switch to the left-most (DLY) position
and quic ee y advance to maximum delay (press UP and
hold it while pressing DOWN and hold until the display
stops changing; release DOWN, then UP). The number
now displayed is the maximum delay time for the cur-
rent sampling rate. It is also the length of any Infinite
Repeat segments that might be captured, and the time
against which the Clock Output rate is referenced.
Assuming that the clock ratio has not been changed
since the unit was turned on, the red CLK indicator
flashing at the upper right corner of the display window
will be flashing at an interval equal to one-half the time
in milliseconds displayed in the window. If the display
reads ‘1600 ms‘’, the CLK lamp will flash every 800
milliseconds. Each flash of this lamp is accompanied by
a pulse at the CLOCK OUTPUT jack on the rear panel.
Since this rate is a fraction of the total available delay
time, itis NOT affected by the UP and DOWN pushbut-
tons, but only by the MANUAL VCO-SWEEP control
(Fig. 2.1, R] and the DELAY X2 pushbutton [Fig 2.1, B].
Now we can begin to program the clock rate to dif-
ferent relationships with the memory size. Note the
presently displayed delay time (all of the programming
to follow is referenced to it) and then slide the SET
MODE switch to the “CLK” position. The display will
read ‘‘] 2’. Now, press the UP pushbutton once and
release. The display will now read "1 4” and the CLK
lamp will flash at twice its previous rate. The clock
period is now equal to one fourth of the delay time
noted before. Further button pushes will cycle the rate
down to 1/64th of the loop length, and then around to
1/1, equal to the loop length. If the button is held down,
the display steps automatically about once per second.
Now try the DOWN pushbutton. The left portion of
the display is stepped through the odd integers 1, 3, 5,
7, and 9. These select the numerator of the fraction,
such as 3/2, 5/8 etc. These ratios are useful for poly-
rhythmic work. Most of the time, however, the figure