Using MIDI VelocityThe velocity value refers to how hard a note or chord is played in a track. A higher velocity number means the note will be played harder. In GarageBand, the velocity is based on real instruments, which sound softer or harder depending on how hard you hit the notes.
Open the Track Editor Window
To edit velocity, first select the track you want to work on. You can click the Solo button so that you only hear this track. Then open up the track editor window by clicking on the Track Editor button.
Select a Note
The Velocity slider will be grayed-out until you select a note or notes that you want to edit.
Adjust Velocity
When you've selected a note or notes to edit, move the Velocity slider to the left or right to lower or raise the velocity value.