Hamburg - Sometimes there's nothing worse than having a song stuck in your head. It's particularly frustrating if you picked up a melody somewhere, but don't even know the artist or title. The internet may ease your pain. Specialized online services are helping identify those nameless favourites.

There are a variety of ways to name that tune. The Fraunhofer Institute for Digital Media Technology records the user singing the tune and tries to identify it against a database of melodies, an approach known as "Query by Humming." The technology was developed at the Fraunhofer Institute in Ilmenau.

Christian Dittmar, director of the group that created the pertinent search engine technology, says that his group had an interesting insight. "A melody may be worth more than a thousand words, but not many people have the confidence to sing the song they want to the sales person in the store," Dittmar says.

That's where Dittmar's internet service comes in. The user sings the song of choice. A recording of the performance is then analyzed and compared with song samples in a database. If successful, the search engine offers a selection of potential matches. The user needs only a microphone; the rest runs via the browser.

Dittmar notes that the search algorithm accounts for poor pitch or wrong notes. The best chances of success come when the user sings the melody using simple words, like "la la la" or "na na na."

"People who sing the text often neglect the melody too much," Dittmar says. Whistling or humming works in a pinch as well.

The technology at present is used at Musicline, a service of the German music industry. The database covers many genres from pop and rock to folk music and classic, but with only 3,500 records it remains undersized.

The Midomi project functions in a manner similar to the Fraunhofer technique, except that the heavy lifting is performed by a community of users. As the participants make their song recordings public, the database grows continuously. The site's operators report that more than 2 million titles have been catalogued. That means that the chances of getting a lead on the melody that's haunting you are pretty good.

The match quality relies heavily on your own singing ability, however. Background noises are a major disruptive factor. For that reason, the page's operators recommend that only one person at a time sing into the microphone. In the event that no matches turn up, the user can also try entering a snippet of lyrics, presuming they've memorized a few lines.

Watzatsong is modelled on a different experience: the quiz show. Users looking for help post a recording of themselves singing the song. The other users in the community then try to figure out which song it is. Proposed solutions are sent by e-mail. Users do have to register to participate in the search process.

For now, those who take advantage of these services should brace themselves for disappointment. "You have to presume a certain rate of failure," says Michael Knott from the online magazine Netzwelt. All the same, because the services are free of charge there's no real risk involved either. Knott recommends another way of tracking down a song as well.

"Almost every radio station now lists the songs they've played on their web sites," he says. So the next time you hear the song, just note the time and broadcaster and half the battle is already won.

(Internet: http://www.midomi.com; http://www.musicline.de/de/melodiesuche; http://www.watzatsong.com) (dpa)