I'll be willing to bet that some folks might have a c.d. player at their booth so you can hear what they sound like...or even a video
player of some sort. Maybe the organizers have already thought of this and made a decision that applies to all. It seems easy enough
to ask them,or just play (with the idea that you will put it away
if asked to stop)

maybe the folks in the lobby could come to an agreement about time
sharing for the booth space..although you might be detracting from
the performer who is on stage...and that is the focus of the event,
to give everyone time to be heard live on stage. Who is organizaing this? sounds like a good opportunity to meet folks (both listeners
and performers)