Having an 'advanced search' feature has been requested tons of times. Since people create new threads instead of searching the forum, I feel forced to copy and paste the same reply in a handful of threads to reach people subscribing to the topic.
I've just added an 'advanced search' interface to my Subsonic mod, see
viewtopic.php?f=4&t=9777&p=50566#p50566.
It allows for combining some twenty different criteria when searching for tracks, browsing all results, and adding all of them for playback. The mod is documented at
http://dilerium.se/musiccabinet/.