Mac OS 8.1 and sound The About Mac OS 8.1 Update file contains the following notes:
Previously, audio management was determined by your computer, now your applications control audio input and output setups. There is a new control strip module which allows easier user selection of sound input source.
On PCI-based Macs: With Mac OS 8.1, the Sound control panel found in the Apple Extras folder can no longer be used to set the sound input source. Use the Monitors & Sound control panel or a new control strip module to change the input source.
On PCI-based Macs Changing the volume in the Sound control strip module will not unmute the computer. If you have selected the mute check box in the Monitors & Sound control panel, you must use Monitors & Sound to unmute the computer.