The default event type \note creates one synth per event, not per pattern or per pattern player. This means there is no safe way to assume that you can store a single synth in a variable and represent all of the pattern player’s activity.
It’s a wrong assumption to begin with.
Pmono creates one synth. But you cannot assume this for every pattern.
Also note that events do not create Synth objects. They create synth (lowercase) nodes in the server but they bypass the Synth (capital) class. So there is nothing created for you that you can set.
Pmono’s synth – you can get the ID using the event’s callback function (Pattern Guide 08: Event Types and Parameters | SuperCollider 3.12.2 Help). Then you can use Synth.basicNew to create an object that you can set.
There is no server object “EventStreamPlayer” – it is strictly language side.
hjh