My second thought:

Sheet music; not a lead sheet. Melody line – Chords --- Right hand for piano—Left hand a chord or possibly a bass line.

Usually the sheet music has a few melody lines that helped make the song popular. Copy those lines by using Step-Record on the keyboard. They can then be used as part of the Acc. or in one of the pads.
Y
ou can also take melody lines out a midi file.
John C.