Amazing man what program are you using?, A lill bit short but I got the same probleme, cant make them more than 3min!!! Keep up the good work man!
I'm using Propellerhead's Reason 4.0, It's complicated but very very flexible. You can download the trial from the official website, but you cannot import MIDI, Save your songs/export and it closes itself down after 20 minutes of use. Anyway, I'm glad you enjoyed it, because I wasn't too sure if I liked it or not... =D