An acronym for Variable Architecture Synthesis Technology. VAST was developed by Kurzweil's Research & Development Institute prior to the release of the original K2000 (1991). Back when most synthesizers utilized one main configuration of oscillators, envelope generators, and filters to produce all their sounds (which is still largely true of many synths today) the idea was to make a synthesizer in which its individual building blocks could be changed and/or connected in different configurations (which they call Algorithms). This, of course, was not a new concept. Modular synthesizers have always had this flexibility. But the problem with modular synths is you have to patch each component manually, which not only takes time, but also requires a great deal of knowledge (experience) in predicting the outcomes. Kurzweil simplified the process by putting 31 useful algorithms under computer control and building the functionality to easily utilize them into their OS. VAST basically is all of those architecture choices as well as the ability to modulate their parameters from a wide list of control sources.
That's the strict definition of VAST. As time went on, however, the concept of VAST began to encompass the many other unique aspects of the Kurzweil OS. Things such as Functions (FUNs), multiple LFOs, ADSRs, and Envelopes can all really be thought of as part of the VAST architecture since they provide unique and very powerful capabilities that are generally not found in most other synths on the market. Many soundware designers who've delved into the depths of VAST claim it is the most powerful overall synthesis engine on the market.
Kurzweil now has a new and improved VAST in the works. Soon the K2600's VAST architecture will include over 100 unique synthesizer configurations. Given the astounding things that have already been done with the current version of VAST (anyone who's heard Daniel Fisher's Dark Side patch knows what we mean by astounding) there's absolutely no telling what will be possible with these new tools.
