Hi Diki
Seeing your post in the Medeastation thread, I thought I would mention that you have been able to use VST instruments with styles since OAS 5, (2003) and they have been greatly expanded in OAS 7.
As for Drums, OAS 6 includes the features mentioned below. (Again they have been expanded in OAS 7)
1. 64 slots for User kits which can be loaded or existing ones edited.
2. Individual drum sounds can be loaded in a kit. (This includes Wave samples from elsewhere)
3. General Editing Features for the whole kit include Volume, Reverb and Delay.
4. For each individual drum sound in the kit, the following can be edited, Volume, Panorama, Dynamic, Reverb, Delay.
Tuning of each drum sound can be in semitones and cents
Envelope adjustment for each drum sound include, Attack, Velocity to Attack, and Decay
Filter controls for each drum sound include, Filter Cut and Filter at velocity
All drum sounds loaded can be up to 24 bit resolution.
As a final point have you had a chance to listen to the old demos I have posted? http://www.synthzone.com/ubbs/Forum37/HTML/014692.html

I am curious to see what you think, as OAS 5/6 was released during the Tyros 1, KN7000 era.
Enjoy whatever you play

Bill