As far as I know it is not possible yet, but It would be an interesting option. Actually using an external midi keyboard you can control song parameters like: start, stop and record. To get what you described there need to be a component that matches your keyboard keys to madtrackers patterns. I am not sure if such a component exists in Madtracker. Such a component should be able to treat the midi-information sent by your keyboard in two different ways. Note based and pattern-based. Interesting Idea though.