Except for very particular cases, even though the search bar works fine for the forum, it gets very difficult to look up a song or an author. When looking up a song, for example, I usually get to a forum topic that says something about the song and no way to get to the MP3 post itself to listen to it or find out who the author is. Is there a good way to look up songs when you don't know the date or author?

If you end up in a quote from a song thread you should be able, via the linked address string (blue bar top), to click back / up to the MP3 thread eg: forums/Audio Review/The Song you cant find/A comment on the song.
Whether there's an easier way to search the site ..... I denno!

I search the AMP through Google.  For example:

http://www.google.com/search?q=site%3Abandamp.com+%22pythonic%22

That searched BandAMP for my song "pythonic".  Notice how the first result is the song.  Basically, you need to prepend your search with "site:bandamp.com" and then surround your search phrase in quotes to get a direct search.  Works perfectly.