If you're interested in controlling audio from your Arduino, you may want to take a look at the PT2322. I've just made a library for this device available. It enables you control 6 channel audio, volume, bass, mid, treble, mute, tone defeat etc. The PT2322 library takes care of the details and makes it easy for anyone to use the device.
Here's the methods available. More details on this blog: http://oddwires.blogspot.com/
int init(void);
void muteOn(void);
void muteOff(void);
void _3DOn(void);
void _3DOff(void);
void toneOn(void);
void toneOff(void);
void leftVolume(unsigned char flv);
void rightVolume(unsigned char frv);
void centerVolume(unsigned char cv);
void rearLeftVolume(unsigned char rlv);
void rearRightVolume(unsigned char rrv);
void subwooferVolume(unsigned char sv);
void masterVolume(unsigned char mv);
void bass(unsigned char tb);
void middle(unsigned char tm);
void treble(unsigned char tt);