I want to quantize not only tempo but velocity, since the first hit on the hi hat by MIDI is too strong. I can do it bar by bar, using the MIDI editor. But is there a way to select and quantize multiple tones to the same velocity?
Holding down ctrl while clicking the mouse on the specific note (or group of notes if you drag the mouse) will select as many midi notes as you require. Velocity is then shown and if all are the same value then reducing the velocity by say 20 will reduce the velocity on all the notes by 20.
Unfortunately if one of the notes you selected had a velocity of (say) 30, it will reduce to 10.
Take a look at the Logical Editor (menu-> MIDI-> Logical Editor).
One of the possibilities I could think of is using the random velocity preset and setting both parameters to the same value. This way all the bars will become equal.
In Cubase 7.5 there is a preset from MIDI » Logical Presets » standard set 1 called fixed velocity 100.
Select your notes and then apply this.
Cubase 5 has an option in "MIDI-Functions-Velocity" which allows you to increase/decrease the velocity of a group of midi notes at the same time.