Virtual nodes is a capability of OMS to update it's published list of synthesizers to applications that use OMS dynamically, responding to the instantiation or de-instantiation of software synths and IAC buses as they may occur in real-time. What this means is that if you instantiate a software synth that uses virtual nodes, OMS sees it and automatically creates a listing for it in the application that can address it. Subsequent instantiations yield further listings, and so on.So far the only real-world call for virtual nodes is within Virus TDM, a software synthesizer that uses Digidesign Mix card DSP chips for its RAM rather than other software synthesizers which use regular computer RAM. If you insert Virus on a Pro Tools track, it immediately becomes available as an output device on any Midi track within Pro Tools. The use of virtual nodes allows one to differentiate between separate instantiations of the same synth (i.e. Virus 1a, 1b and so on) and instantiations of different synths (i.e. Virus 1, 2, 3 and so on). As soon as the synth is removed and thus deactivated, it is also removed as an available output device within OMS and is no longer published to Pro Tools.