"It's Only Heaven" - Hurricane
"My Immortal" - Evanescence
"It Can't Rain All the Time" - Jane Siberry
"Isle of the Dead, Op. 29" - Sergei Rachmaninoff
"Goodbye Blue Sky" - Pink Floyd
"When the Crowds are Gone" - Savatage
and of course "Rain (Female Vocal Version)" by Mai Yamane from the Cowboy Bebop OST: