Stereo Source; Mono Source - Alesis ModFX Phingr Reference Manual

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Using the Phlngr
How the controls work inside the flanger
Picture it this way: there's a block of audio in delay memory
several milliseconds long, always being loaded with new audio
from the input jacks. A "pointer" picks up this audio at some
particular point in the delay for playback. If the pointer stays in
one place, it's just a static delay line—and when you mix the very-
slightly delayed output with the original input, you get a comb
filter (phase cancellations at certain frequencies, additions at
others). If you move the pointer back and forth in this block
quickly, the pitch will change: higher as it moves towards the start
of the block, lower as it moves towards the end of the block. This
also changes the shape of the frequency response, when it's mixed
in with the original signal.
The [DEPTH] control sets how big the "block" of audio is, from
start to finish. The [RATE] control sets how quickly the playback
pointer runs from the start to the finish of the block and back
again. The Modulation Type (Triangle, Pattern, etc.) sets how
smoothly (or not) the pointer moves through the block. The
[CENTER] determines where the pointer starts—beginning, end
or center—at the start of a cycle. The [REGEN] control sets how
much of the output of the pointer is fed back to the input of the
block, and whether that output is in phase (+), or out of phase (-).
Flanging in stereo

Stereo source

When you have a left and right input plugged into the Phlngr, it
behaves like two separate flangers that are synchronized. If a
piano goes into the left input, it comes out of the left output,
flanged, without mixing with any signal going through the right
channel (unless the TYPE is set to DEEP MONO, see p. 33).
This discrete stereo operation is important for stereo instruments,
and if the Phlngr is part of a stereo effects chain (for example,
following an Ampliton in autopan mode).

Mono source

But, mono sources can be transformed into a pulsating stereo
signal when they're connected to the LEFT/MONO input to
achieve a particular dramatic effect. If nothing's connected to the
right input, the LEFT input is automatically sent to both left and
right flangers. If you set the TYPE switch to CONTRARY
STEREO or ASYNC STEREO, the different outputs of the two
sides will broaden the stereo perspective from any mono source.
Especially for listeners on headphones, the result can be quite
dramatic.
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