Many newer systems do away with the audio cable altogether. Recent versions of Windows support audio-CD playback using digital audio extraction, which lets the PC read digital data directly from the drive and perform the necessary digital-to-analog conversion. The biggest drawback of digital audio-CD playback: If there's a headphone jack on the front of the optical drive, it won't work when you play a CD. (which is why most newer CD\DVD players no longer have the headphone jack on the front of them !)
Put a CD into the second drive and play it -- you should hear the music without any connector - as they have said the interface bus now handles the connection so the cable is no longer needed ! IF you do find a need for it you can purchase a Y-splitter so that the one connector can have 2 drives connected to it.