Hi @user25 Sorry for the late reply.
Playable instruments are not ran via interactive blocks but rather the Instrument Override API call in the game engine. See here for unity: ExampleScripts | Reactional Docs
You essentially send along instrument name, x and y (pulse and pitch) velocity etc. and it will behave the same as the Playable instrument demo square in the composer interface.
I am making pretty huge changes at the moment to composer and the plugins which I hope to go live in the next couple of weeks. This includes instrument spatialisation in game engine, instrumentation snapshots, a live subtractive synth, a maxmsp kind of node plugin for making own synth to use in game, and a ton more improvements.