Apple Logic Pro 8 - Manual (Page 565)

Chapter 25 Mixing 565
 Pan checkbox: The panorama setting of all member channels is linked. As per
volume, their initial relationships are maintained.
 Send 1 to 8 checkboxes: You can link the Send knobs individually for Send slots 1 to 8.
Different initial levels will be maintained.
A Note on Group Automation
Any group member can act as a master for mix automation of an automated
parameter, such as volume. When an automation parameter value is written, the
corresponding value of all other group members is also written, depending on their
automation mode (Touch or Latch, for example). The data is written individually for
each channel. As a result, you can disable the group later, without affecting the
automation of any group member—and can obviously edit or change channels
individually, once removed from the group.
Disabling Groups Temporarily (Group Clutch)
It is possible to temporarily disable all group parameter links—in order to change the
volume of an individual channel, for example.
To temporarily disable all groups:
m Choose Options > Group Clutch (or use the Toggle Group Clutch key command, default
assignment: Command-G).
As long as the group clutch is active, all group displays will change color—from yellow
(normal) to a light gray (clutch active, all groups temporarily disabled).