Kurzweil K2500RS, Руководство музыканта

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Program Mode and the Program Editor
Using the Program Editor
6-5
Algorithm Basics
The basic deÞnition: an algorithm is the ÒwiringÓ (signal path) of a sample to the audio
outputs, through a series of digital signal processing (DSP) functions that you select. The
K2vxÕs algorithms are the core of Variable Architecture Synthesis Technology. The DSP
functions are synthesis tools (Þlters, oscillators, etc.) that you assign to the various stages of the
algorithm. The DSP functions you choose determine the type of synthesis you use.
Each of the 31 available algorithms represents a preset signal path. You canÕt change the path of
the algorithms, but you can select different algorithms, and assign a wide variety of DSP
functions to the individual stages of each algorithmÕs signal path. Take a look at Algorithm 1 in
the diagram below. ItÕs one of the simplest algorithms.
Algorithm|1||||||||||||||||||||||||||||||
|||||||||||||||||||||||||||||||||||||||||
errR®rrterrR®rrrrrrR®rrrrrrR®rrterrR®rrt |
d PITCH| gk HIFREQ|STIMULATOR||||| gk AMP||| gh
cvvvvvvbcvvvvvvvvvvvvvvvvvvvvvvbcvvvvvvb |
The DSP functions are represented by the rectangular blocks. The horizontal arrows indicate
the ßow of the digital signal from left to right. They represent what we call the ÒwireÓ of the
algorithm, the actual physical path that the signal follows through the algorithm. Selecting
different algorithms can be compared to connecting different DSP functions with different
wiring diagrams.
Think of the left side of each block as its input, and the right side as its output. Depending on
the algorithm, the signal may split into two wires, enabling part of the signal to bypass certain
portions of the algorithm. Split wires may rejoin within the algorithm, or they may pass all the
way through as split signals. If the last block has two wires at its output, we call it a double-
output algorithm. If it has one wire, itÕs a single-output algorithm, even if there are two wires in
earlier portions of the algorithm.
The Þve downward-pointing arrows indicate the Þve realtime control inputs to the DSP
functions. There are usually Þve inputs, each of which has its own page within the Program
Editor. (Algorithms 26-31, which use hard sync oscillation, have only four inputs; you can read
about hard sync functions on page 14--50.) Each of these pages has several parameters that can
modulate its related DSP function. Often a single DSP function will have more than one input.
ThatÕs why some blocks are larger, and have more than one arrow pointing to them. Each
function can be independently controlled by a variety of sources (the Control Source list),
including LFOs, ASRs, envelopes, programmable functions, and external MIDI.
In Algorithm 1, the signal ßows Þrst through a one-stage DSP function that controls the pitch of
the samples in the keymap. In fact, the Þrst DSP function in each algorithm
always controls
pitch, even though it doesnÕt apply in every instance. Similarly, the last DSP function always
controls the Þnal amplitude of the signal. It can be a one-stage or two-stage function. In
Algorithm 1, itÕs a one-stage function.
The second, larger block indicates a single three-stage DSP function, meaning that it has three
control inputs that can be adjusted to modulate the signal.
Once again, you canÕt change the wiring path of an algorithmÑyou can simply select a
different algorithm to get a different path. And within each algorithm, you can assign a large
number of different DSP functions to each of the Þve control inputs. The diagram below, for