When you merge MIDI regions:
All events from each individual MIDI region retain their original time positions.
The new (merged) MIDI region adopts the name and track of the first (along the timeline) of the original MIDI regions.
The Transposition, Velocity, and Dynamics region parameters—if not identical in all selected regions—are normalized before the merge. This means that all parameter values are written as data changes for each region before the merge. The parameters of the newly created (merged) MIDI region are all set to neutral (default) values.
If one of the region parameters (the Transposition value, for example) is set identically in all selected regions, that value is preserved in the Region Parameter box for the merged region, and the events remain unchanged from their original values.
Note: Be aware that the individual MIDI channels of events (if applicable) are replaced by the MIDI channel of the current track Instrument channel strip.