All Music has a function that allows you to search through their database by theme. Wes wrote about AMG's many surprises.

I have recently bumped into a good site - moonlightcinemanetworks.com while searching in internet on the topic.

You can't quite search song themes, but it will come up with every song with your chosen word in the title, who recorded it and what album it's on. It also has loads of information on the artists, and reviews of all the recordings.