BARCELONA, Spain -- King Ferdinand and Queen Isabella gave Christopher Columbus a hero's welcome when he returned to the royal court in 1493 after his first voyage to the New World. Thousands gawked as Columbus and his crew paraded down the main street of Barcelona with Indians, parrots, gold nuggets and other bounty.

At Mass in the Basilica de Santa Maria del Mar, refrains from the musical instrument associated with divinity -- a pipe organ -- solemnized the event and seemed to bring heaven's blessings to Earth. It is a role that Europe's great pipe organs have played for centuries on occasions grand and humble -- from coronations to weddings, baptisms and funerals.

But now a mysterious epidemic of organ "leprosy" is sweeping Europe, corroding pipes and threatening to silence some of the continent's most renowned instruments. The European Union has mounted a major effort to save them, even though it is not yet known whether modern central heating, air pollution or something else is causing the problem.

"Organs were the personal computers of their era, the most complicated devices made by humans," said Carl Johan Bergsten, a research engineer at Gothenburg University in Sweden who also is an organist. "They combined so many different disciplines, both technical and artistic. It makes the organ a central and indispensable part of our common European cultural heritage."

Bergsten heads a team of chemists, metallurgists, music historians and other experts funded by the EU that has taken on the acronym COLLAPSE, short for "Corrosion of Lead and Lead-tin Alloys of Organ PipeS in Europe.

Most of Europe's more than 10,000 historic organs are enormous devices, often several stories high with hundreds or thousands of hollow pipes up to 64 feet long. They feature multiple keyboards for both hands and feet, and pneumatic mechanisms that send streams of air coursing through the pipes. Each pipe produces a unique sound, ranging from the bright, piercing blare of festival trumpets to the mellow lilt of soft flutes to the chest-throbbing boom of double basses.

Mozart called the pipe organ "the king of instruments" due to its complicated design, its wide variety of sounds and the considerable skills needed to play one. And while the pipe organ often is associated with worship services, the instrument had a 1,000-year history before it appeared in churches.

An engineer named Ctesibus of Alexandria who lived in the 3^rd Century BC gets credit for inventing the organ, the loudest mechanical device on Earth at the time. Called an "hydraulis," it used tubes connected to a "wind reservoir" but little is known of its construction. The hydraulis was first used in ancient Roman sporting events and other spectacles. The first pipe organs as we know them today appeared in churches and monasteries around 800 AD.

The problem of corrosion first gained widespread public notice in the 1990s, when some of the largest pipes in the 1467 Stellwagen organ at St. Jakobi's Church in Lubeck, Germany, fell silent. It turned out that 1,500 of the organ's pipes were severely damaged, and even though some were more than 500 years old, the corrosion seemed to have started only during the past few decades.

As news spread from St. Jakobi's, other churches inspected their organs and identified similar problems. The basilica of Santa Maria di Collemaggio in L'Aquila, Italy, found 80 percent of its pipes were corroded. The situation was so bad at a cathedral in Bordeaux, France, that church officials feared their organ would collapse under its own weight.

The organist at St. Jakobi's asked Bergsten for help, which eventually led to the founding of the multinational COLLAPSE team.

At this point, no one is sure why or how many of Europe's historic organs are affected, although Bergsten's group has learned that corrosion also affects modern organs.

COLLAPSE is comparing one group of "healthy" organs with another group of "sick" ones in an effort to identify the factors responsible for corrosion. They have recorded humidity and temperature in churches, and they have probed samples of healthy and diseased pipes with high-tech instruments including X-ray fluorescence and atomic absorption spectroscopy.

Early findings fingered modern central heating as a prime suspect.

Many of the corroded organs had unexpectedly high levels of acetic acid. Acetic acid is found in oak, which often is used to build or restore structural elements in pipe organs. Researchers suspected that the higher temperatures produced by central heating were drawing more acetic acid out of the oak. But they have since learned that many organs restored with oak do not show corrosion. Corrosive air pollutants remain a suspect, as well.

Metallurgical studies offer interesting clues.

Italian members of COLLAPSE have found that all affected pipes in Italy were made with a small amount of tin, barely 2 percent. Tin used to be expensive, and organ builders in Central Europe tried to economize by using a German alloy that contained little of the precious metal.

In the United Kingdom, on the other hand, where corrosion is rare, tin was mined locally and was less expensive. Organ builders used up to 20 percent tin in organ pipes, Bergsten said.

But even as modern studies suggest tin might help organ pipes fight off corrosion, "tin plague" has been identified as a culprit in the past. Scientists long have known that tin slowly disintegrates into a powder at low temperatures, and superstitious parishioners used to think organ pipe failure was the devil's work, an attempt to silence instruments regarded as God's own.

Obviously, COLLAPSE researchers have their work cut out of them, as they try to learn not only what causes pipe corrosion but also how to prevent and treat it.

"We hope that the results of this study will be useful in particular in the Central and Eastern European countries with their enormous heritage of around 10,000 instruments," Bergsten said. At present, amputation is the usual treatment for severe corrosion, which often occurs in the base, or "foot" of a pipe, according to John Pike Mander, of Mander Organs in London. His family has been building and restoring pipe organs since the 18^th Century.

"If it is only the feet which are affected, one can often cut off the foot above the damage and make a new pipe foot of exactly the same shape and material as the old one," he explained. The new section often can be tuned to produce a sound very close to the original.

Transplantation is the only cure for pipes on the verge of collapse.

"When the pipes have collapsed, there is no other way to solve the problem than replacing the historic pipes with modern ones," Bergsten said. "And the historical sound quality will be lost and the sounding cultural heritage is forever gone."