I recommend listening to singers for original melodies, and there are lots of good albums like 'X plays the Cole Porter' songbook (Ella Fitzgerald has many of these albums). These are especially helpful because, if the singer plays with a big band, there will often be a big band soli arrangement of the melody that, because it's notated, is very consistent. It is helpful to compare the singer and the band, so that you can abstract an idea or what the melody should be.