Depending on the units in question, they might have a sound active setting via DMX. Look in the manuals/DMX charts for them.
If confused, list the fixtures for us and hopefully we can help more.
Little side story with regards to dimmers and things other then filament lights plugged into them. A local company rented a school 13 Mac 700s in my area not to long ago. This is all fine and dandy, but the school in question I use to work at and know it doesn't have the power for 13 Mac 700s. So I asked the company if they got a generator. They said no, the school returned the order 2 weeks early (was a 4 week rental) and when the company checked the fixtures, all the lights ballasts were fired. The school plugged all the Mac 700s into dimmers. Real nasty repair bill to say the least. So don't plug things other then lights with just filament lamps in them.