Apple Logic Express 7 - Manual (Page 456)

456 Chapter 18 Synchronization
Audio Sync Mode
This is where you define how each individual piece of audio hardware should be
synchronized to an external time code master.
Not all audio hardware can work in every sync mode described below. This is
particularly dependent on whether or not the hardware’s sample rate can be
controlled.
MTC Continuous
Audio regions are started in sync, and the sample rate is continuously regulated in
accordance with variations in the time code master signal. Even very long audio
regions stay in sync in this mode.
MTC Trigger
Audio regions are started in sync, but are then played at a constant sample rate,
regardless of any variations in the time code master signal. Logic always uses the set
nominal sample rate (44.1, 48, 88.2, 96 kHz).
This mode is suitable when it is vital to retain the absolute pitch of a recording. If the
speed of the time code master deviates from the nominal value, you may need to split
long Regions into shorter sections.
External or Free
Logic has no influence on the sample rate. The audio hardware is responsible for
ensuring that the position and sample rate of audio Regions match. This mode is only
advisable if you are sure that the word clock and time code master are running in
sync—by using an external SMPTE/wordclock synchronizer, for example.
MIDI
Transmit MIDI Clock
The checkboxes activate transmission of MIDI Clock. The pull-down menus determine
the MIDI output ports for the MIDI Clock signal.
The two Destinations allow you to specify discrete MIDI ports.
Every time you start, “Song Position Pointer” (SPP) is also sent.
As not all devices can process SPP, the MIDI system realtime “Continue” message is also
sent. The exception to this is when you start at position 1 1 1 1. In this situation, the
realtime “Start” message is sent.
MIDI Clock can easily be sent with other normal MIDI events (notes, controllers). When
using multiport MIDI interfaces (such as the Unitor8), better timing is achieved by
sending MIDI Clock to All ports, rather than to several individual ports.