There are a few quite useful (and seem to me unique) engines:
http://lyricsrobot.com/ (song lyrics search)
http://www.musicrobot.com/ (MIDI file search)
http://www.tabrobot.com/ (guitar tabs search)
It would be very nice to see their implementation in favorite browser.
Dzmitry Drazdou
Domo arigato, Mr Roboto
Bots attack!
http://mycroft.mozdev.org/search-engines.html?name=lyricsrobot
http://mycroft.mozdev.org/search-engines.html?name=musicrobot
http://mycroft.mozdev.org/search-engines.html?name=tabrobot