Logic: Making note velocities (and other values) the same

1. Select the notes you wish to affect and make sure they are selected in the Event List editor. You can do this conveniently by selecting them in the piano roll editor and then opening the Event List editor ( Windows/Event List) and the same notes will be selected.

2. Hold option/shift and then in the Event List editor click, hold and scroll the values of the notes you wish to turn to similar values (such as velocity, length, note number etc)

This will make the values the same.