Chapter 17 Funs; The Mechanics Of Control Sources; Unipolar And Bipolar Control Sources - Kurzweil K2600 Musician's Manual

Chapter 17
FUNS
The name ÒFUNÓ is an abbreviation for ÒFunction.Ó FUNs are a series of equations that you can
use to modulate control-source signals.
WeÕve discussed various control sources throughout this manual, from the physical controls like
the Mod Wheel to the software control sources like LFOs and attack velocity. You can assign
them to affect your sounds in all sorts of ways.
The FUNs take the control sources one level further. By setting up a FUN as a control source,
you can mix the signals of two control sources, and perform one of 50 functions on the combined
signals. The result of that function becomes the new control source value. Because they can
radically change their combined input values, FUNs can have a profound effect on your sounds.
You may Þnd that experimenting with the various FUN equations gives you a better idea of
their effects than reading the explanations. Although thereÕs some serious mathematics behind
the FUNs, the most important consideration is how they affect your sounds. The more you play
around with them, the better youÕll understand how powerful they are.

The Mechanics of Control Sources

WeÕll return for a minute to the notion that the K2600 is an integrated system consisting of a
MIDI-driven sound engine and a MIDI-driven effects processor. The sound engine responds to
MIDI messages received at the MIDI In port and from the front panel, as does the effects
processor.
The K2600Õs control sources use their own internal signal format for interpreting control
messages and communicating them to the sound engine. Every control source sent from your
MIDI controller to the K2600Õs sound engine is translated to a value in the range from -1 to +1.
This consistency enables the sound engine to process control source signals very efÞciently.
Conversely, the K2600Õs internal control source signals are translated to MIDI values before
being sent to the MIDI Out port.
A control signal value of 0 represents minimum effect; itÕs equivalent to the control source being
turned off or disconnected. A control signal value of +1 represents the maximum positive effect
of a control source, while a value of -1 represents the maximum negative effect of a control
source.

Unipolar and Bipolar Control Sources

There are two kinds of control source signals: unipolar and bipolar. A unipolar signal has a
value between 0 and +1. A bipolar signal has a value between -1 and +1.
A switch pedal is unipolar; its control signal value will never go below 0. Since itÕs a switch
control, it has only two possible values: 0, which corresponds to off or minimum, and +1, which
corresponds to on or maximum. When you depress your MIDI controllerÕs sustain pedal, for
example, it sends a control signal value of +1 to the K2600Õs sound engine.
Continuous controls can be unipolar or bipolar. Consider your MIDI controllerÕs Mod and Pitch
Wheels as examples. Normally, the Mod Wheel affects the K2600 as a unipolar control source; it
sends a control signal value thatÕs interpreted as 0 when itÕs fully down, and values interpreted
The Mechanics of Control Sources
FUNS
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