Blast from the past: is that a ghost in your pocket or are you just tuned in to chakugoe? (Upfront).

LEONARDO DA VINCI IS said to have been so enamored of his portrait Mona Lisa that he carried it everywhere with him on his travels. Five hundred years after it was painted, the Florentine lady's silent, enigmatic face continues to mesmerize -- but what would the Renaissance master think if he knew that today her voice is being heard all over Japan?

"I'm Elizabeth, also known as Mona Lisa," she says with a sultry Italian lilt when telling mobile phone users they have a call coming in. Mona is one of several historical figures brought to life by mobile content developer Index for subscribers to NIT DoCoMo's i-mode and au's EZweb cellular services. Leonardo's sonorous voice can also be downloaded, along with that of 9th-century Japanese scholar and patron deity of students, Sugawara Michizane, who tells anxious users, "You definitely passed!"

But these chakugoe, or ringtone voices, aren't just any old synthetic computer sounds. Through a process called Montage Voice Technology, Index and partner Japan Acoustic Laboratory have created vocal timbres they say are reasonable approximations of what the real thing would have sounded like.

"We analyze very carefully and measure the body parts of great historical persons like Mona Lisa," explains Index spokesman Katsuhisa Oda. His firm and Japan Acoustic Lab, run by acoustics expert Matsumi Suzuki and known for authenticating voice recordings such as those of Osama bin Laden, set up a virtual company called Japan Ringing Tone Laboratory to analyze pictures of people of the past and, so to speak, re-voice the dead.

The researchers analyze finger size -- which can play a key role in determining height -- and other characteristics like skull shape to come up with an educated idea of what historical figures really sounded like. The process takes about a month, according to lab researcher Yumiko Higuchi. (Incidentally, Mona Lisa, aka Lisa Gherardini, was apparently 168 cm tall.)

Higuchi describes plans to add new voices to coincide with seasonal events. Heian era women of letters, Sei Shonagon and Murasaki Shikibu, were slated for Valentine's Day, and a multilingual Santa Claus who sounds a bit like Darth Vader came out at Christmas. Another idea is to have users ring in the New Year with the sound of traditional Buddhist bells. Reaction to the service, one of many at Index's Eraberu J-POP site (www.ejpop.net), has been positive since it was launched last year, says Oda.

Users pay from [yen]90 to hear the voices of the past. They can also have a prehistoric Tyrannosaurus roar in their pocket to notify them of a call. Other chakugoe planned by the lab include Beethoven and Napoleon, as well as tengu goblins, magic foxes and even the sizzle of tempura.

The Eraberu J-POP site has over 6 million users to date, which has helped make Index one of the country's leading mobile content providers. Building on its success, the firm recently set up bases in Beijing and London as part of a drive to acquire and deliver popular content worldwide. Who knows -- if foreign users turn on to chakugoe, many more voices from beyond the grave could be pressed into service for the mobile living.

Tim Horn yak is a Tokyo-based freelancer and a regular contributor to J@pan Inc.