Apple Logic Pro X - Manual (Page 310)

Chapter 10 Create a song arrangement 310
MIDI regions must be on the same track or on adjacent tracks. When you join MIDI regions, the
joined region takes the name (and track) of the first original region. If the Transposition, Velocity,
and Dynamics region parameters are different for the selected regions, they are normalized
before being joined. (This means that all parameter values are written as data changes for each
region. The parameters of the joined MIDI region are all set to neutral (default) values.)
No mixdown
If several (mono or stereo) regions on the same track are from the same original region, and in
the same relative positions, no mixdown occurs. In this case, a single region is created.
No mixdown occurs when you join two regions on tracks that are panned to opposite sides, as
the two resulting mixdown files would be identical to the original audio files (in the areas used
for the regions).
If several overlapping audio regions on a track are selected, no mixdown occurs. You are asked
to create a new audio file, which takes the name of the first region on the track. The selected
regions are then mixed together, with no changes to volume, and without clip scanning.
Genuine mixdown with Clipscan
If you combine audio regions from two or more tracks, the current pan and volume values for
the individual tracks define the pan and volume settings in the new audio file.
If you want to combine both sides of a stereo audio file (a mono channel on each of two tracks),
first set the pan controls of the component mono sides to hard left and hard right, respectively.
Following the digital clipping scan (Clipscan) and completion of the mixdown, Logic Pro replaces
the previously selected regions with one region that contains the entire mixed-down audio file.
You can use the Edit > Undo function (Command-Z) to restore the original audio regions, if you
change your mind about the mixdown. If you do so, you are asked if you want to keep, or delete,
the newly created mixed audio file. If you keep it, it remains in the Project Audio Browser, and
can be further used and processed.
During a mixdown, the 32-bit resolution Clipscan function ensures that the highest possible level
is maintained, without clipping.