Lexicon PCM 42 - 4.2 Special Applications of Long Delay; 4.2.1 Layering and Infinite Repeat; CANON EFFECT SETTINGS

The prevalent technique for placing the image of a
source within a stereo sound field is to pan the signal
from left to right, relying on the amplitude difference
between the channels to create the perceived image
position. But certain advantages can be realized by
using delay in conjunction with, or even in place of,
conventional panning. Imaging by means of level differ-
ences alone works well only for listeners located mid-
way between the two loudspeakers; at off-axis loca-
tions, the image shifts toward the loudspeaker from
which the sound arrives first, a psychoacoustic
phenomenon known as the Haas effect.
The Haas effect arises from the brain’s ability to iden-
tify similarities between sounds arriving at the ears at
different times. Any sound sufficiently similar to one
which arrived at the ears within the previous 30 milli-
seconds will be perceived as a reflection of the original,
and the brain will localize the source as coming from the
direction of the first arrival. The greater the delay be-
tween the two arrivals, the more the source’s apparent
location shifts toward the first one.
The Haas effect can be transformed from a problem
into an asset by using it in a controlled way to shift the
apparent position of a sound source in the stereo field.
With the PCM 42 connected in the Basic Stereo Setup
as shown in Fig. 4.3, simply adjust the delay to achieve
the desired degree of apparent offset of the sound
source. Delaying the sound in the right channel will
cause the source to shift to the left, and vice versa.
Delay times of 5-30 ms are most useful; above 30 ms,
the delayed sound begins to be perceived as a separate
echo, destroying the effect. (For additional information
4.2.1 Layering and the Infinite Repeat Mode
DELAY XZ LEWER FEEOGACK FUER
SET MODE
OL me CLK
ot = OF cox
O rgd
“y %
on this subject, consult Lexicon Application Notes AN-2
and AN-3.)}
4.2 SPECIAL APPLICATIONS OF LONG
DELAY
4.2.0 Introduction
The class of musical applications for long delay
{greater than one second) is somewhat distinct from the
applications discussed above. These are closely akin to
results obtained with tape loops, but the special quali-
ties of digital delay and the unique features of the PCM
42 allow much greater freedom than is attainable with
tape, even without the PCM 42's obvious advantages
over a couple of high-quality open-reel recorders in
compactness, ruggedness and cost. Many techniques
previously confined to home or studio can now be used
in live performance.
In general terms, the use of very long delays in music
produces a type of ‘canon’ or polyphonic effect by
superimposing the audio image of previously performed
phrases over current material. With no feedback, only
one previous phrase will be audible, but if feedback is
added, each delay period will repeat more than once
before it dies away. With large amounts of feedback,
the performance will pile up, one phrase over another,
until input to the delay line ceases or the unit is placed
into the infinite repeat mode. At full feedback and max-
imum delay time (with the optional memory extension)
the decay time of the PCM 42 exceeds 3 minutes!
PARAL GEPTH WAVEFORM
RY
DELAY
Figure 4.5-| — CANON
This option begins to make use of the multilayering potential of the PCM 42. The delay time should be set at the max-
imum available; for machines with the memory option, the MANUAL VCO-SWEEP control will be at about 10:30
o'clock.
Using this overlay technique, it is possible to create
compositions and rhythmic beds in real time that can be
trapped via infinite repeat, or continuously evolved by
adding new notes as older ones are tading out. When
the repeat function is used, the resulting backgrounds
may be soloed over without entering the notes into the
delay loop.
19
itis important to be aware of the nature of the Infinite
Repeat function in the PCM 42 in order to make full
usage of the looping technique. WHEN THE INFINITE
REPEAT MODE iS ACTIVATED, THE FULL MEMORY
IS ALWAYS UTILIZED. The length of the segment cap-
tured in memory is independent of the delay tap
selected by the UP and DOWN pushbuttons. It is af-