Apple Logic Pro 8 - Manual (Page 852)

852 Chapter 37 Working With Plug-in Latencies
If you are recording audio, another strategy would be to disable the Software
Monitoring checkbox in the Logic Pro > Preferences > Audio > Drivers tab. This would
necessitate monitoring your recording via an external mixer. When Logic Pro is not
providing software monitoring of incoming audio, it can correctly position audio
recordings—even when full delay compensation is active. Obviously, you can’t use
external monitoring when recording software instruments.
Note: As Logic Pro has no direct control over the audio outputs of external devices,
plug-in delay compensation can not work for MIDI tracks that trigger external sound
modules. If you activate full plug-in delay compensation and insert latency-inducing
plug-ins, external MIDI signals will be out of sync with the delayed audio streams.
Logic Pro allows you to circumvent this issue with the External Instrument plug-
in: Insert it (as you would insert a software instrument plug-in on instrument channels)
to route the audio outputs of your external MIDI devices to the inputs of your audio
hardware—and monitor them through Logic Pro. This enables you to compensate for
the delays of any audio streams coming from MIDI devices during playback.