At the beginning:
What's Love Got To Do With It

When Cat's bit starts:
Stargirl

When Julia gets on the train:
Midnight Train to Georgia

Cat's middle bit where it starts to get exciting:
Pirates of the Carribean

When Julia goes to where she goes to [you'll have to read it to find out!]:
I'm Leaving on a Jet Plane

Rob's bit:
Love Lifts Us Up [where we belong]

Rob's other bit and Cat's last bit:
A Little Piece of My Heart

The ending:
All You Need Is Love