I've done this before but cannot recall how to change 1 MIDI note's velocity all at once.  Using BFD Drums, and want to change the velocity on the high-hat that's say 110 down to 85. I can highlight the entire row but when I do properties, it's only changing the single note hit I've clicked on.

Assuming you are using an X series version of SONAR 
 
select the note row required 
then in the inspector set the velocity to your required value
 
sorted.

Ah found it - Highlight the row - Scale Velocity and set the two values.
 
Thanks!

You can also hover your mouse over one of the selected notes and alter velocity with your mouse, although it won't set them all to a specific value.
 
You can also use the Event Inspector to make all kinds of changes to MIDI notes. Check out the Event Inspector Editing video on my site: http://www.garrigus.com/
 
Scott

--
Scott R. Garrigus - http://garrigus.com - SONAR X2 Power! - http://garrigus.com/?SonarX2Power
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Draw them in with the line tool (straight across the track from start to finish)

And don't forget the Velocity midi plugin!!