A computer subsystem of a computer includes a CPU (120), RAM, display (110), storage device (114), input device(s), and a digital-audio generating IC (130). A CD-ROM subsystem of the computer includes a CD-ROM drive (138) and CD-ROM control buttons (142) for controlling CD-ROM drive's operation while playing audio CDs. An audio-interface IC (102) of the CD-ROM subsystem couples a bus of the computer subsystem to the CD-ROM drive, and to the control buttons. The audio-interface IC, in one operating mode, relays commands and data between the bus and the CD-ROM drive. A second operating mode permits turning the computer subsystem off while the audio-interface IC autonomously responds to the control buttons and transmits commands to the CD-ROM drive for playing an audio CD.