Some confusion appears to have arisen between the VST 2.0 and ReWire technologies. Since more and more applications will appear over the coming months, supporting one or other of these technologies, here is a basic comparison of the two:
VST 2.0 technology means that a ‘virtual studio instrument’ be it a synth, sampler or drum machine, must be implemented as a Plug-In. This Plug-In will normally be displayed in a single window where the parameters can be adjusted within that window by the user. When so implemented, the synth’s parameters are then automated by the host application. The MIDI information is only stored on the host’s MIDI tracks and is sent direct to the Plug-In synth. The latency between pressing a note on the Keyboard and hearing the synth sound is exactly the same as the latency of the sound card. In the case of Cubase the delay on playback is zero as the latency is fully compensated for in the Cubase Audio engine. If you have a low latency ASIO sound card then this is not really a problem. If, however, someone is using a sound card with 750 ms of latency, then simply using a MIDI device to monitor the recorded sound will solve the problem.
ReWire technology allows a link between two independent applications. In this case, the device on the other end of the ReWire link does not need to be in any particular format. The other application can do whatever it wishes with its application. The basis of the ReWire technology is that the other device gets a chance to have outputs in the host application’s Mixer and have its transport controls (if any) linked to the host (currently only Cubase supports this). In ReWire 1.0 (like you have seen in ReBirth) the sounds the other application makes are created by its own ‘song’. The MIDI tracks of Cubase are not used to control this. Actually ReWire 2.0 technology also makes this possible, but is not yet available in any product.
Hope this helps.