Is there anything better that a SSR when working with audio signals?
Your SSR isn't switching audio, which it would be bad for.  It is switching the AC power to the lights, so that's fine.  Since you are apparently switching the power on and off rapidly, a SSR is a good choice.

You are apparently using a audio signal to control the SSR somehow.  That's also fine if it's done right.  It sounds like you're just feeding the amplified audio signal into the SSR input.  That will turn it on when there are large positive peaks, which will very roughly make the lights come on when the audio is loud.  There are better ways to detect loudness.  To avoid switching the SSR on and off too rapidly (could cause lots of radio interference), you should be using zero-crossing SSRs.  These turn on and off at zero crossings, regardless of when the input signal goes on and off.

Of course zero crossing SSRs might not give you the visual effect you want.  You'd have to describe what you really want the lights to do as a function of the audio signal for us to suggest a good method.