then U have to erase the notes manually..
my advice to U is to have:
1 main sequence where U have the complete beat, lets say you have an 4 bar sequence with drums, bassline, melody etc
and whenever U want to make an variation in your song just
copy your main seq to, lets say seq 2.
on seq 2 you can remove parts or add other parts that U just want to have as an variation
whenever You are satisfied with your adds and removes you can just enter song mode and chain the different sequences togheter.
aight? good luck