How do I change the velocity on a bunch of selected notes in a midi clip?
 
Thanks,
 
Tom

There are a number of methods.
 
Use the inspector in the Control Bar to set them to a specific value.  You can change by percentage or + and - Values here as well.
 
Use the CAL script VARYVEL.CAL to change to a range of random values between fixed parameters.

There is the scale velocity option. Manually edit in the event list, PRV or Staff view.
 

From the piano roll you should be able to just drag the velocity up or down by placing the cursor right above one of the notes. The event inspector might let you type in the desired velocity as well but I have not tried that.

Like others have said:
Select notes and drag the velocity bars in the PRV or use event inspector to set all selected notes to the same value.

If you want a linear change, from greater to lesser or vice versa, select whatever notes you want changed, and use "process" - "Scale velocity".   Then the change will be applied either as percentage of what is already set, or directly as a midi velocity number (check or do not check the percentage tick box).      I do this often, so I set the letter "V" as a keyboard shortcut for scale velocity.     The "curve" is fixed, unfortunately: it is linear by time, but it will still get you nearly what you want, I think.