"Je kent die settings behoorlijk vanbuiten..." 
Logic Pro handleiding blz.1178 :
Using External Synchronization
When you first open Logic Pro, manual synchronization mode is automatically turned off, and Logic Pro is in Internal Sync (master) mode. Activating the Transport bar’s Sync button synchronizes Logic Pro to the chosen synchronization source.
If Logic Pro is running by itself (no devices or applications capable of synchronization are in use), or is acting as the synchronization source, it is the synchronization master device. In this situation, the Transport bar’s Sync button should not be activated. The Transport bar Sync button is not displayed by default.