The Kids Get It
The clearest early example is documented in The Kids Get It: a young listener makes visual work in response to music; JQD receives that object and reworks it, allowing the response itself to become new source material.
Audience as secondary maker
Parallel Play differs from ordinary interactivity because the recipient does not simply choose among options prepared in advance. The desirable outcome is another independent object, interpretation, performance or mutation.
Relation to transmission
The concept gives a concrete social form to a broader principle found throughout the writing: a work can transmit successfully even when the result is not faithful. Continuation may matter more than obedience.