Velocity is the parameter that is responsible for the volume of a specific MIDI note.
When you record a MIDI track using your MIDI controller that is equipped with touch response/velocity sensitivity feature, it assigns a value between 1-127 on each MIDI note depending on how hard you played the keys. However, if you manually input the notes on the Piano Roll, the default velocity is set to 100.
Manually adjusting the velocity gives you complete control on how you’d like a specific MIDI note to be played, depending on the loudness or softness that you’d like to achieve.
To adjust a MIDI note velocity, you can refer to the screenshots below:
Click the “V” icon or press Alt + Ctrl/Cmd. The lines inside of a MIDI note correspond to the velocity value assigned to a specific note.
A numeric velocity value will appear once a MIDI note has been clicked. You can adjust the velocity value by dragging up or down.