Apple Logic Pro 9 - Manual (Page 814)

If a channel strip or an external (touch-sensitive) automation controller is touched, the
existing track automation data of the active parameter is replaced by any controller
movements—for as long as the fader or knob is touched. When you release the controller,
the automation parameter returns to its original (recorded) value. The time required by
a parameter to return to its previously recorded setting is set via Logic Pro > Preferences
> Automation > Ramp Time.
Touch is the most useful mode for creating a mix, and is directly comparable to “riding
the faders” on a hardware mixing console. It allows you to correct and improve the mix
at any time, when automation is active.
Latch
Latch mode basically works like Touch mode, but the current value replaces any existing
automation data after releasing the fader or knob, when Logic Pro is in playback (or
record) mode.
To finish, or to end parameter editing, stop playback (or recording).
Write
In Write mode, existing track automation data is erased as the playhead passes it.
If you move any of the Mixer’s (or an external unit’s) controls, this movement is recorded;
if you don’t, existing data is simply deleted as the playhead passes it.
Warning: Be careful with Write mode (and its settings), to make sure that you don’t
erase your pan, bus, and plug-in automation data by mistake, if your intention was only
to erase Volume fader information.
To determine the type of data that should be erased
1 Open Automation preferences by doing one of the following:
• Choose Logic Pro > Preferences > Automation (or use the Open Automation Preferences
key command).
• Click the Preferences button in the Arrange toolbar, then choose Automation from the
pop-up menu.
814 Chapter 28 Working with Automation