It is also possible to use the lower 4 holes as the main notes and use the notes one octive higher as intervals to play concurrently. like lower C ( higher cegc), lower E ( higher egce), same for all blow notes for G & C. But for draw notes, you can only do D ( higher df), G (higher fa), B ( higher ab), D ( higher bdf) etc
Octaves is possible for all blows notes CEGCEGCEGC, and draw notes DBDFA. So that makes,, CDEGBCDEFGAC. It is easy to do it smoothly with some practice.