Decoupling capacitors on IC powered from split supply?

I'm working on an audio amplifier and have been having good results thus far. I'm wondering though if a certain part of my circuit is doing anything. I'm using an op amp IC to amplify my audio signal and have it powered on a +-9V supply. I have a cap on Vcc, does it benefit me to have on on Vss also? They're connected to the virtual ground of the circuit.