Diminution and Augmentation

How do I stretch or compress a given set of midi notes rhythmically in the key editor. For example, compressing 4 subsequent whole notes into 4 subsequent quarter notes or anything in between.

This is easier to do in the Project Window than the Key Ed. Select the Arrow tool with the option Sizing Applies Time Stretch. Now just drag the Part’s lower right corner to resize it. If you want you can have the Part open in the Key Ed as you do this to see the results more closely.