In the Staff View I see a lot of blank space at the top next to the now time and note value 'window'. This means additional, functionality could easily be added there for any note(s) selected. In particular, 1-click buttons. 
 
Why is this important? Well, the step sequencer can take a user only so far. At some point, 'feel'/emotional weight needs to be added to parts by modifying the velocity and length of certain notes. 
 
Also, allow users to define the default value(s) to meet their personal preferences.