Select multiple regions in the Score Editor
When Additional Score Options is selected in the Advanced preferences pane, you can select multiple regions in the Score Editor either from the Region inspector or in the score display.
Select more than one region in the Score Editor
Click an instrument name in the column between the parameters and score, to select all regions for that track (including regions on different tracks that are assigned to the same software instrument channel), at the current display level.
Note: The instrument name column is displayed only if View > Instrument Names is selected.