Melody Catcher
MelodyCatcher makes it easy to enter a melody
(even if you don’t know how to play the piano)
and search for it on the Internet!
Massive and ever increasing volumes of music are available online. As long as titles or names of composers, performers or artists are known, it’s easy to find related information. If only the melody is remembered, however, common search engines fail to provide any results. Many ideas and concepts of melody finders or Music Information Retrieval (MIR) Systems have been described. For a good overview see: http://en.wikipedia.org/wiki/Music_information_retrieval#MIR_applications
Since results of the Melodycatcher show playable MIDI files and their sources, it also is a MIDI search engine by melody input, that might help to further disclose the large online MIDI world.