audience participation controls

[Paul Perry]

......a performance/musician has asked if there are any cheap 
ways to enable say 5 or so members of the audience to jam with 
the band from the dancefloor, triggering samples, adjusting
synths etc.
All I can think of is TV remotes.....can these operate on diff frequencies?
....suppose I could nobble them to use different buttons on each........

I think somebody once said torches on LDRs.....I don't think the
ambient light interference would allow this, but perhaps laser pointers,
though this is getting too expensive (not everything you throw into an
audience comes back). Ultrasonics?

all ideas, experiences welcome

Paul Perry Melbourne Australia