6-4
Program Mode
VAST Program Structure
VAST and KB3 Programs
It is important to understand the difference between VAST programs and KB3 programs.
VAST
programs contain up to 32 layers, each of which contains a keymap or KVA oscillator.
Keymaps consists of a number of samples assigned to a particular keyboard range. KVA
oscillators use powerful DSP to generate a range of simple and complex waveforms (see
Editing
VAST Programs With KVA Oscillators
on page 6-53
for more details.) See
VAST Program
Structure
below for more details on VAST programs.
KB3
programs use a much different architecture. There are no layers or algorithms, just a set of
oscillators (designed to emulate the tonewheels in a Hammond Organ) that start running as soon
as you select a KB3 program. See
KB3 Program Structure
on page 6-6
for more details on KB3
programs.
VAST Program Structure
You might want to take a look at
Figure 6-1 on page 6-5
, which depicts the hierarchy of a VAST
program, from individual samples all the way up to setups, which can contain up to 16
programs.
Every VAST program contains at least one layer. A layer consists of a keymap and an algorithm
for processing the samples contained in the keymap. Each sample is a separate digital recording
of some kind of sound: musical, vocal, industrial, any sound at all. Individual samples are
assigned to specific key ranges (from A 2 to D 3, for example), and are also assigned to be
triggered at specific attack velocities. These assignments constitute the keymap.
When you trigger a note, the PC3A looks to the keymap of each layer of the currently active VAST
program(s) to determine which samples to play. The sound engine then fetches the requested
samples and generates a digital signal representing the sound of the samples. This signal first
passes through the DSP functions that make up the algorithm. It then passes through the PC3A’s
effects processor, and finally appears—with some level of effects applied to it—at one or more of
the audio outputs.
The layer is the VAST program’s basic unit of polyphony, that is, each layer constitutes one of the
128 voice channels the PC3A can activate at any time. If you have a program that consists of two
layers covering the note range from A 0 to C 8, each key you strike triggers two voice channels.
Note:
One exception to this structure is when using a KVA oscillator, the sound source for that layer is not
derived from a keymap, but is generated at the algorithm stage (though keymap information is still used to
set key range and maximum amplitude.) After this, the structure is the same as described above. See
Editing VAST Programs With KVA Oscillators
on page 6-53
for more details.
