Apple Logic Pro 8 - Manual (Page 917)

Chapter 39 Working in the Environment 917
Logic Pro will enclose all selected objects in a frame with a gray background.
If some of the objects selected when creating a macro have cables leading to
unselected objects, these cables will be deleted when the macro is created. A warning
will notify you of this. In this situation, the macro is made from a copy of the original
selection of objects, and the original collection of objects remains unchanged.
Macros are limited in size—the limit is dependent on the memory usage of the
individual objects within the macro. This limit is typically between 100 and 200 objects.
You can nest macros—a macro can contain other macros as objects.
To unpack a macro:
m Double-click any empty (blank) section of the macro object.
This reverts the macro back into its component objects and cables.
Macros have a lot in common with standard Environment objects—you can connect
cables to and from them, they can be resized, they have their own parameters and
icon, they can be chosen as destinations in the Arrange window track list, and they can
be copied or dragged between Environment layers (including between projects).
Defining a Macro’s Input and Output
As a macro is a collection of objects, individual objects need to be specified as the
macro’s input and output. This can be done in two ways: by name or by default.
 If you name one object “Macro-In”, and another “Macro-Out”, these will automatically
become the macro’s input and output.
 If there is no object named “Macro-In”, the upper-leftmost object will become the
macro’s input.
 If there is no object named “Macro-Out” then the lower-rightmost object will become
the macro’s output.
Cables leading into the macro deliver events to the macro’s input object, and cables
leading from the macro’s outlets carry events leaving the macro’s output object.