Tool Window: Introduction to MIDI and Computer Music: Center for Electronic and Computer Music: Jacobs School of Music

Reason: Changing Notes with the Tool Window

First, be sure you know how to edit notes in the Sequencer.

Open a clip for editing.
Window > Show Tool Window opens the Tool Window. Click on the wrench-and-screwdriver icon to see the Sequencer tools.
Each category of tool — Quantize, Pitch, Note Velocity, Note Lengths, etc. — has a reveal triangle that lets you open and close its settings. Be sure these first four categories are open.

Quantize snaps selected notes to the nearest vertical grid line. (See quantize controls in picture above.)

Value sets the equally spaced time intervals of the grid lines used when quantizing: 1/16 for sixteenth note, 1/4 for quarter note, etc.
Amount is how closely the command will move a note to the nearest grid line.
Random adds a random offset to the note, up to the maximum number of ticks given.

To use any of these tools, first make a selection of notes in the Edit/Arrange pane of the Sequencer. Click with the arrow tool in a blank area of the editor, and drag to include the notes you want to change.
With the notes still selected, adjust the settings in one of the tools, and click the Apply button just below the settings.
For example, if you want to scale all the velocites to higher values, look at the Note Velocity settings, and change the Scale percentage to a number greater than 100. Then click Apply. Notice that the velocity bars beneath the notes have changed.
To use the Note Lengths and Legato Adjustments tools, you have to understand how timing works in the Sequencer.
You don’t actually have to be in Edit Mode to use these tools. Just click on a clip in the Sequencer to select it, then apply a tool: it will affect all the notes in the clip.