IBM Aptiva Hardware Handbook page 28

such as a MIDI (Musical Instrument Digital Interface)
keyboard.
When your headphones are plugged into this jack,
use the volume control on the CD-ROM drive to
adjust the volume of the headphones. This volume
control adjusts the volume of the headphones, but
not the speakers. If you want to turn the speaker
volume down while using the headphones, use the
volume control on the speaker.
•
On all multimedia models of the IBM Aptiva PC, the
headphones can be plugged into the Out jack on the
sound card on the back of the system unit. This is
the same jack you plug your speakers into. You must
disconnect your speakers to use this jack with your
headphones.
If you plug your headphones into the jack on the
sound card, the headphones will pick up all sounds
generated from your computer and any external
devices connected to the computer, such as a MIDI
(musical) keyboard. The headphones will also pick
up sound coming from a CD in the CD-ROM drive.
When your headphones are plugged into the jack on
the sound card, you must control the headphone
volume through the volume control in the multimedia
software on your computer. You cannot control the
headphone volume from the volume control on the
CD-ROM drive. To access the multimedia software, look
note:
in either the Soundblaster group or the Multimedia
Utilities group in Windows Program Manager.
When using this jack, a few sounds may not be audible
through the headphones, such as the beep when you
turn on your computer.
18 Controlling the volume on multimedia systems
.