Hello! I bought a brand new Yamaha portable grand, which can display two lines of music for MIDI files from a USB device. So, I downloaded some of my favorite songs and put them on the device, hoping the screen would display the parts for the leading melodies of the song. Rather, most of the songs showed some of the obscure bass or background parts, that I didn't really care to play. Is there any way I can adjust which instrument parts will be displayed? Thank you so much in advance!!