Instead of a D.J., a Web Server Names That Tune http://www.nytimes.com/2003/01/23/technology/circuits/23next.html?pagewanted =all&position=bottom WHAT'S NEXT Instead of a D.J., a Web Server Names That Tune By ANNE EISENBERG A SONG and its name are easily parted, as anyone knows who has listened to a tune on the radio and then waited in vain for the announcer to identify it. Now some companies are using a technology that can name that tune as it plays, promptly displaying words like "Take Five by the Dave Brubeck Quartet" in text on an Internet radio or cellphone. The systems are sensitive enough to identify not only names and artists within a vast range of recorded music, but also different versions of a piece done by the performers, even when the differences are slight. At the recent Consumer Electronics Show in Las Vegas, for instance, Royal Philips Electronics demonstrated a prototype of an Internet radio that was not only capable of naming the band Pearl Jam as its music streamed past but also distinguishing a version of a tune that it played at a concert in Verona, Italy, from the same tune recorded in Milan. "To our ears the two versions sound the same," said Ton Kalker, a mathematician at Philips Research in Eindhoven, the Netherlands, who led the team that developed the rapid identification system. "But the technology is sensitive enough to make a distinction." The technology that spots the mystery tune in products from Philips and other companies is called audio fingerprinting. It is based on the premise that every performance of a song has unique audio characteristics - for example, a certain relationship of neighboring high and low notes over a minuscule slice of time. Represent those relationships in numbers, and you have a code that shows a particular version of a song, and no other. "Audio fingerprinting works by creating a mathematical description of some of the unique features of a song," said Dr. Richard Gooch, deputy director of technology at the International Federation of the Phonographic Industry, a trade organization based in London. The fingerprints are stored on a server. When the server is asked to identify a tune - for instance, a song playing on Internet radio - software matches a snippet of the tune, expressed in code, with the whole coded version of the song stored on the server. Some companies offer fingerprinting technology to identify not only streaming content but the contents of audio files and traditional radio broadcasts as well, Dr. Gooch said. His group and the Recording Industry Association of America have recently investigated many audio fingerprinting systems to see if they might benefit the recording industry. Dr. Gooch said that the technology stood up even to the most difficult conditions - poor loudspeakers, highly compressed streaming files or broadcasters who speed up songs slightly to make room for commercials. "We've found that even when broadcasters tweak a song or compress it," he said, "so long as you can still hear it, the systems can extract a description of unique characteristics in the song," quickly matching the description with the database to identify the track. The steadily improving technology has been used commercially in business applications since at least the early 80's, he said, for example, in the music business to identify broadcast performances and then pay royalties to rights holders. Given the popularity of digital music, consumer applications of the technology are probably inevitable, Dr. Gooch said. "Audio fingerprinting is accurate, robust and runs in a sensible amount of time," he said. "It really works." Shazam Entertainment, based in London, already offers British consumers an audio fingerprinting service linked to cellphones. Users dial the service and then hold their phones up to the tune that is playing, say, on the car radio. Shazam has a database with fingerprints of 1.6 million tunes. It matches the incoming fingerprint with its database and within 30 seconds sends a text message back to the phone identifying the song. "We have most any popular song that has been recorded," said Philip Inghelbrecht, founder of the company and director of its content. "So long as the CD is commercially available, we will have it." In the future, manufacturers of electronic devices may offer audio fingerprinting to people who want to organize music collections stored on their hard drives, said Vance Ikezoye, chief executive of Audible Magic, a company in Los Gatos, Calif., that offers its own patented audio fingerprinting technology. "It's hard to manage music if you don't have the correct information for every song in your collection," he said. Companies have used different techniques to create the unique code that constitutes a fingerprint. At Philips, for example, Dr. Kalker said, he and colleagues created the code by breaking each tune into 10-millisecond snippets. Then they calculated the differences in the loudness of adjacent frequencies in the snippet and how those differences changed over time. They repeated the process every 10 milliseconds to extract code over the entire length of the song. Then, when an Internet radio detected the song streaming through it, it sampled the song and sent the sample along for pattern-matching. "The whole process takes about three seconds," he said. "So even a dumb AM or FM receiver can tell you a lot about what you are listening to." Dr. Gooch suggested that fingerprinting systems would eventually be common on car radios. "When every car has its own digital audio player," he said, "people will want to know the name of the song they are listening to displayed on the dashboard." Mr. Ikezoye of Audible Magic said that people who used the company's system need not worry about violating the rights of music publishers. Although Audible Magic maintains a big database of popular copyrighted music, he said, the fingerprints are not the actual songs, but summaries of factual measurements describing the sound. "The original sound can't be reconstructed from the fingerprint," he said, "so storing and sharing fingerprints does not represent an infringement of the copyright." If the technology catches on in consumer applications, radio listeners may one day have an antidote to a common problem cited by Cary Sherman, president and general counsel of the Recording Industry Association of America: "Radios often don't bother to tell listeners what they have played," he said simply.