Make your own music controlled lights

Would this concept work if I just used the output Pos and Neg (red and black) outputs from a surround sound system? Correct me if I’m wrong but, I’m thinking instead of removing the speaker, I would just use a couple wires that are connected to the surround sound receivers output, yeah?

Hi,
I recently tried this tutorial and I can’t seem to get it to work. I do admit I made some adjustments from the tutorial as I could not get the Crydom D2W203F Solid State Relay, so I had to use an Osaka SK04A280 Solid state relay insead. I think it’s basically the same except it handles up to 4amps instead of 3.5. But I’m not sure, does it make a difference? Also the Christmas lights I use are LED lights that have a small controller that makes it blink, flash, and stays on. So whilst having it stay permanently on, I still could not get it to pulse to the beat. What do you think is the major problem, the Lights or the Solid State Relay?