wiring a music interface to a relay

I have a Bass Reactor unit which is used to modulate LEDs to “the beat of the music”.  Here’s a link to it for reference. http://store.gaugemagazine.com/index.asp?PageAction=VIEWPROD&ProdID=1980

 What I’m trying to do is have the Bass Reactor unit fire the LEDs via a Bosch Automotive relay.  I have tried every possible hookup I can think of but nothing seems to work.  The Bass Reactor unit flashes the light by interrupting the ground circuit of the LED, not the positive.  I tried wiring the relay using the ground side of the Bass Reactor as a trigger but to no avail.  I tried the radio shack relay – part# 275-248 hoping this would work but it did not either.  Note: When the Bass Reactor is switched to be solid on, everything works fine through the relay.

Honestly, I’m at my wits end here and I’m hoping someone on the forum can help me out and perhaps make a suggestion or two.

Thanks in advance,

Gary

What does it being a motorcycle have to do with anything?  It's a 12 volt system.

I could really use some good advice here.

Thanks,

Gary

No problem.  Thanks in advance for your help!

Gary