OS ANGELES — A supersized packet of French fries, Medusa on a bad hair day, the aftermath of a Great Quake: the architect Frank Gehry's huge pipe organ facade, the visual centerpiece of his new Walt Disney Concert Hall, has been called all of these things. No conventional description will do.

"Frank wanted it to look unlike any other organ you'd ever seen," said its creator, Manuel J. Rosales. In that, everybody agrees, he and Mr. Gehry succeeded.

Now Mr. Rosales is trying to make it sound unlike any other organ you've ever heard. And that is an acoustical and engineering challenge as formidable as any organ maker has faced.

Racing to meet a July deadline for the organ's debut (the hall opened last October, to general dazzlement), the builders have had to design a tonal palette that would be able to complement the sounds of the Los Angeles Philharmonic, but also stand on its own in solo programs.

They had to adjust the size, sound and volume of each of its 6,134 pipes to suit the acoustics of the four-tiered, 2,265-seat hall. They had to engineer a way to make huge display pipes in bizarre shapes, anchor them securely into the rest of the structure, and yet allow them to sound normally. And since earthquake faults run beneath downtown Los Angeles, they had to make the organ quakeproof.

The pipes and other parts were built to Mr. Rosales's specifications in 2001 and 2002 by the Glatter-Götz Orgelbau company of Owingen, Germany. Glatter-Götz delivered the pipes early last year, after building the steel framework that holds them all up, and completed the installation in June.

The 40-ton organ looked finished when the hall opened, its curving stainless-steel shapes billowing like sails around an auditorium that does not have a single right angle. The pipes swoop and curve, too, with the flowing Douglas fir interior of the hall.

But that left the time-consuming task of tonal finishing, and by early May, Mr. Rosales said, it was only about three-quarters done.

Still, he promised that it would be ready for a national convention of the American Guild of Organists in early July, and for its public debut on Sept. 30: a recital by Frederick Swann, followed the same weekend by Todd Wilson and the Los Angeles Philharmonic in the "Organ" Symphony (No. 3) by Camille Saint-Saëns and the Concerto for Organ with Percussion Orchestra by Lou Harrison.

Pipe organs in the 17th century were among the most complex mechanisms humanity had devised. Like organs of that time, this one has mechanical connections, wires and wooden slats, between the keys of three of its four keyboards and the valves that admit pressurized air into the pipes, dozens of feet above the organist, making them sound when a note is played.

But unlike antique instruments, the Disney Hall organ also uses electric action — a system that activates magnets to pull open the valves when the keys are pressed.

Electric action allows the organ to be played from a movable remote console (four keyboards, pedalboards and stop controls) on the orchestra platform, 20 feet below the pipes and about 40 feet in front of them. With the two separate control systems, two organists can even play the organ at once.

Mr. Rosales, a Falstaffian figure at 56, is president of Rosales Organ Builders Inc. of Los Angeles, highly regarded by many organists, and competitors. He said he wanted the organ to be complete with keyboards, not playable in concerts only when stagehands wheel out the mobile console, as in places like Severance Hall in Cleveland or Symphony Hall in Boston.

All but 2 of the 126 visible pipes in Mr. Gehry's unusual facade design are functional, speaking ones. The biggest are about 32 feet long. These are the lowest notes of the 32' Violonbasse stop in the pedal organ, and they make a bowel-shaking rumble.

Some of the large curved wooden shapes are the resonators of another low pedal stop, the much louder 32' Contre Basson. The brass pipes pointing directly out at the auditorium are the bold trumpets of the "Trompeta de Los Angeles," one of many stentorian voices this organ will have.

Almost all the rest of the thousands of pipes, as big and thick as trees or as small and thin as pencils, are lined up conventionally straight up and down in rows in the five divisions or sections of the organ, mounted on a strong steel frame. Most of these pipes, made variously of oak and pine or of a bright tin-lead alloy, are contained in spacious chambers with thick wooden walls and louvered shutters that can muffle the sound or let it swell louder when the organist opens them by pushing on foot pedals that look like accelerators.

Behind the wild facade pipes, the organ towers three stories. Almost daily, Mr. Rosales and his longtime associate, Kevin Gilchrist, climb ladders up into the organ and toil for hours in the quiet of night after the orchestra has gone home, trying to coax just the right sounds out of each pipe.

Building the organ, which has 72 stops lined up in 109 ranks, or sets of pipes, one for each of the 61 notes on the manual keyboards and the 32 notes on the pedalboard played by the feet, started with the acoustics of the hall. Sound reverberates in it for about two seconds when all the seats are filled, according to the building's acoustician, Yasuhisa Toyota, of the Tokyo firm Nagata Acoustics Inc.

Rich and resonant was how Mr. Rosales wanted the organ to sound, so after conferring with Mr. Toyota long before the hall was built, he specified larger "scales" — a higher proportion of diameter to length — for the backbone pipes of the organ.

The hall's acoustics turned out to be all that was promised.

"The hall is particularly favorable to individual sounds," Mr. Rosales said. "The orchestra has also been learning it doesn't need to play loudly to be heard clearly and distinctly."

The same went for the organ pipes. The metal ones were made for Glatter-Götz in Portugal, and once they got to Los Angeles, they and the wooden pipes, made by the German company, had to be "voiced."

For this, Mr. Rosales and Mr. Gilchrist have tools much like a dentist's picks and spatulas — in fact, some are dentist's tools, which they use to work on the "mouth" of a pipe.

"It's like asking the pipe to say `aaahh,' " Mr. Rosales explained as he got ready to work.

Some kinds of pipes take more time than others. "I could spend 40 to 60 hours just on one set of string pipes," narrow ones whose keen tone is reminiscent of violins and cellos, Mr. Gilchrist said.

With a pipe of the 315' Grande Tierce stop sitting on its windchest saying "aahh" for him, Mr. Rosales pressed the soft metal of the lower lip of the mouth inward, making it narrower so that less air would pass through and it would be softer when it was played.

After a day or two, when all 61 pipes of that stop finally had just the right tonal quality, he would tune them with a brass device called a cone. The cone can either close in the top of a metal pipe to make it flatter in pitch or flare out the top to sharpen it.

The 315' stop Mr. Rosales was working on reinforces the fifth natural harmonic of the 32' pipe series, two octaves and a third above the fundamental tone.

Other stops have names like Flute or Piccolo or Trompeta that describe the sounds they produce, often only suggestive of the instruments they are named after. Pulling out all the stops — with stopknobs on the vertical panels on either side of the keyboards — produces a powerful roar of sound.

Stops like the Trompette, Bombarde and Hautbois are called reeds, because a metal reed vibrating against a hollow tube in the foot of the pipe produces the tone, amplified by the length of the pipe above the foot. The giant curving Contre Basson pipes in the facade are some of the largest reed pipes in this organ.

Remembering Mr. Rosales's initial resistance to the idea of bending and curving those big pipes, Mr. Gehry said: "It was hard to get him to do it. I said, well, when a clarinetist plays clarinet, he raises it up and lowers it, so why not?"

Craig Webb, the Gehry associate who did much of the design work on the facade display, said: "We didn't want vertical pipes, and Manuel explained that metal pipes would sag and bend if they weren't vertical. Then we said, `Can we bring wooden pipes out and match them to the redwood cladding of the room?' He said, `Why not?,' and then we said, `Can we lean them, since they're not metal but wood?' "

Mr. Rosales admitted that this gave him pause, as did the idea of bending and curving the pipes that emerged as Mr. Webb produced scale models.

"The reaction of the organ world and other organ builders was `This will be your ruination, and it will set back organ building 100 years,' " Mr. Rosales said.

Finally he took a deep breath and decided to go ahead anyway. "I had to trust that the design would win people over," he said. Glatter-Götz had no problem curving the long Douglas fir pipes at the factory, as long as the curves were gentle, and, as Mr. Rosales put it, "The pipes had no issue with that."

But the design also had to be earthquakeproof.

"Each pipe is anchored with a steel-plated foot," Jonathan Ambrosino, an expert consultant involved in the project, wrote recently in The American Organist magazine. "Twin stainless-steel support rods project from the organ's skeletal frame and connect near the top of each pipe to an interior steel plate. In turn, each top connection is hinged, allowing the pipes a limited degree of motion during an earthquake. Nothing quite so daring and unusual has previously existed in organ building."

J. Michael Barone, host of the weekly "Pipedreams" national radio program produced by Minnesota Public Radio, was also a consultant on the project, which Mr. Rosales said cost about $3 million, $1 million of it a gift from Toyota Motor Sales USA Inc.

As some of the stop names show, the organ design includes the tonal colors of French romantic as well as classic organs. There are also German sounds, and an entire division with a Spanish name, one original to Mr. Rosales — the Llamarada, which is designed to be heard in dramatic orchestral climaxes.

"I hope it won't be too strong," Caspar von Glatter-Götz, head of the company that built the organ, said half-joking, in a telephone conversation. "The organ was a popular instrument for half its history. Only in the last 800 years has it been associated with the church. I hope that by bringing it to big halls and secular places we can change that."