Thank you for the help @David-Healey ! This worked perfectly.
I would like to include a few additional notes. There is a good bit of information that needed to be passed to each sampler. The interface relayed this information to controls in the MIDI Processors via interface control callbacks in the following format:
scriptProcessor.setAttribute(controlIdx, value);
In the onNoteOn block, Message.ignoreEvent(true) and Message.makeArtificial() were called. The note IDs produced by the Synth.playNote() command were stored in an array that was referenced when turning off the notes with Synth.noteOffByEventId() in the onNoteOff block.