Apple Logic Pro 7 - Manual (Page 604)

604 Chapter 18 Tempo
The Tempo Fader Parameter box displays Pitch Bend events as the In-definition (by
default). This allows control of Logic’s tempo with your keyboard’s Pitch Bend wheel.
The Effect on Recording
This way, new tempo track data can be recorded “intelligently”. The original tempo data
will only be erased in areas that actually contain tempo changes.
The Effect on Playback
If the tempo fader is moved during playback or recording, all data defined in the
tempo list is switched off, until the sequencer is stopped.
The Effect on External Sync
Movements of the tempo fader are ignored when external SMPTE sync is active.
The tempo fader can therefore be used to deactivate the sync reference during
playback or recording, if you wish.