The choppy sound you're getting is because of the lack of legato. Go into the options panel and change the sustain pedal/legato control to normal midi control (the second option) and you should be able to get legato out of the strings/brass/woodwinds instead of held notes. Make sure and overlap the notes so that they legato properly. The amount of overlap depends on taste. Also, bowstrokes are controlled by the sustain pedal controller as well. Pedal up = up bow, pedal down = down bow for all sustained string instruments.