hello, i have a roland vs 1680 and i stopped using it for awhile so i forgot my tricks. 1 thing i forgot was how to create a song, so i've been using up one of the songs that is usually no longer than 1 hr and adding to it. now i'm up to 7 hours and i ran out of hardrive space. how can i erase the first 5 hours since i'm still working on the last 2? thank you for your help