Choose Window > Advanced Tools. Click the MIDI tool .
Select the region whose playback data you want to edit. Click to select one measure, SHIFT+click to select additional measures, drag-enclosed to select several on-screen measures, click to the left of the staff to select the entire staff, or choose Edit > Select All.
Choose MIDI > Continuous Data. Click Channel Pressure; click OK.
If you want to edit only one staff, double-click the highlighted region to enter the MIDI tool split-window. Drag through the display area above the notes whose Channel Pressure you want to edit.
Edit the selected region by choosing the appropriate command from the MIDI tool menu. Choose Set To to specify a uniform value for the Channel Pressure of all notes in the selected region. Choose Scale to create a gradual change in Channel Pressure values over the selected region. Choose Add to add a positive or negative amount to all notes in the selected region. Choose Percent Alter to change the Channel Pressure values in the selected region by a percentage of their original amounts. Choose Limit to specify a maximum or minimum Channel Pressure value for the notes in the selected region. (See also Set to dialog boxScale dialog box; Add dialog box; Percent Alteration dialog boxLimit dialog box.)