2000 - 2016
OAS
OAS started off in its basic form in 2000 and used the Creamware Scope sound engine for its main sounds, a Yamaha XG card for the Drums & accompaniment with a plug in OX 7 hardware board for its drawbars, after a year or so, support for Akai samples was added along with an option to purchase the NI B4 Hammond VST, in addition all versions came with Steinberg Cubasis as standard to allow the use of other VSTs.
Demo (OAS 4)
https://app.box.com/s/yb8651a4qk8x74gqvtpx2rgf9nid6n0iThe next big development came with OAS 4.1 which dispensed with the Yamaha XG card and added a 2nd DSP card with a more powerful computer, thus all sounds (Including drums & accompaniment) except OX 7 were produced by the Creamware Scope sound engine.
OAS 5 was another big step as it introduced a brand new OS which could take better advantage of the new hardware; thus more sounds and features became available and this was effectively the coming of age for OAS instruments.
OAS 6 added extra features and sounds but was not exactly a must have.
OAS 7 was another major change that added lots of new sounds and features, but did require a hardware upgrade as well; in addition the previous Creamware Scope sound engine was dispensed with and replaced with a version of the sound engine used in Steinberg’s Hypersonic VST, (For compatibility all the old sounds were converted into the new format so that uses old pre-sets could still be used) it also had a fully integrated VST Host.
Details of the OAS changes up to V7 can be found in this PDF document here
https://app.box.com/s/8c6keigylnl8oeqthrll There were 47 revisions to OAS 7 finishing at OAS 7.1-R47 released in 2014, all of which added new features, sounds, styles and options + bug fixes, (With too many to list here) but a big update came in 2007 when the old OAS arranger system was replaced with the OAA (Open Art Arranger) style system, which also included Chord control and Remote Octave options, (For comparison purposes the programmers guide for the OAS style arranger was around 6 pages, whereas the OAA had its own 58 page manual) it was so different that it required a completely new style format to be created. (Naturally they included the ability to play old format styles so that uses could still use their existing styles)
One of the big plays was the ability to play and edit Tyros 2 styles natively, (The OAA had more features available than the Tyros 2 at the time) but unlike other manufactures that substituted sounds when they converted a T2 style, Wersi created their own voices to mimic the T2 style voices (Including Mega voices) so that when the style was played, it sounded like the style was made for the OAS instrument rather than sounding like a converted style, or that someone had just stuck a T2 on top of the instrument, which as it has a completely different sound engine meant its sound characteristics were quite different and it was difficult for a lot of users to merge the 2 sound systems so that they sounded as one. (Some went for both anyway, having both a T2 (And later models) on top of the instrument as well as using the T2 styles on-board)
The OAA like OAS got continual updates over time adding new features.
Demo of the 2007 models: Music for Everyone by Mark Whale
https://app.box.com/s/ljupx7jrabpmu2rw1oos The big downside of the OAA was that apart from half a dozen or so new styles, all the old factory styles were left in place requiring the user to edit them or create new ones with the new features themselves, (Not the easiest of tasks) however in 2011 Music Store that now owned Wersi since 2010, introduced Styles 2011 (Which used the new features and replaced the old factory styles) as one of the new options for existing users to purchase.
OAS Instruments were finally retired in 2016 after 16 years of production and development and were replaced by the OAX range which launched in 2014.