MADRID -- The sound of pounding feet spilled into the street from a studio in the flamenco quarter here last week as Noche Flamenca rehearsed ''La Plaza." A few miles away in a suburban arts center, Nuevo Ballet Español ran through its own dances, the strumming of guitars filling the hallways.
These popular, prize-winning troupes will both perform in World Music's Flamenco Festival this week at the Cutler Majestic Theatre. Noche Flamenca appears today and tomorrow, Nuevo Ballet Español makes its Boston debut Saturday and Sunday. Yet they interpret the fiery and soulful dance very differently: Noche Flamenca proudly maintains tradition, while Nuevo Ballet Español definitively breaks with it.
Flamenco, which combines Arab, Jewish, Gypsy, and Spanish elements that developed in the southern region of Andalusia more than 200 years ago, has undergone enormous changes over the last 10 years. Its practitioners, increasingly exposed to a wide variety of influences, have begun introducing new steps, music, and themes -- everything from tap dance to pop songs to antiwar references.
As a result, flamenco's popularity has greatly increased in Spain, where many have had their fill of traditional flamenco and prefer new, more choreographed interpretations. To most aficionados of the traditional form, of course, this is heresy, an outrageous commercialization of the dance. The heated debates might surprise most Americans, who are accustomed to thinking of flamenco as only one style.
Julio Bravo, the chief dance critic for the Spanish newspaper ABC, likes both styles and takes a cynical view of the controversy. ''Yes," he said, ''there are two types of flamenco. As always. Good and bad."
The charismatic dancers Angel Rojas and Carlos Rodriguez, who established Nuevo Ballet Español in 1995, are in the vanguard of the ''new" flamenco. In ''Flamenco Directo," the widely praised work they'll present in Boston, they fuse the multiple dance styles they've been trained in: flamenco, ballet, jazz, classical Spanish, and modern dance. Though in many works dubbed new, choreographers fail to successfully fuse the various elements, Rodriguez and Rojas succeed in ''Flamenco Directo." ''We want to create our own vision," Rodriguez said. ''We feel flamenco should change for the new generation, which hears, sees, and enjoys all kinds of music and dance and has different concerns than those of the past."
Meanwhile, Martin Santangelo, the American who founded Noche Flamenca here in 1993 with his wife, the dancer Soledad Barrio, sees no reason to update flamenco. ''There is so much variety in the art already," said Santangelo, who is almost scholarly in his approach after years of flamenco dance training and study in Spain. There is, he says, ''so much still undiscovered from the past that there's no reason to embellish or modernize it. The rhythms and songs can give rise to so many interpretations. It's about eternal and fundamental feelings and emotions."
Oddly enough, watching these companies prepare for their US tours, the similarities between them are more apparent than the differences, perhaps because they both emphasize the soulfulness, ''the duende," at the heart of flamenco. Rodriguez, a fan of contemporary choreographers Jiri Kylian and Nacho Duato, confessed to returning increasingly to his flamenco roots. ''It's like coming back to earth," he said.
Before rehearsing ''Flamenco Directo," his dancers warmed up by rapidly tapping their feet, moving in circles as they tried out different sequences of steps. Young and energetic, the women wore sweatshirts, long skirts over tights, and low-heeled flamenco shoes, their hair pulled into ponytails. The men performed their routines in jeans, T-shirts, and flamenco boots. They'll all be transformed for the show: In most sections, the women wear vividly colored, form-fitting dresses with ruffled trains, while the men don crisp, stylish white shirts and black trousers.
Calling for the music, Rodriguez and his group began the piece in two lines, first one moving forward, then the other replacing it, the excitement building with every click of their castanets. Rodriguez often chooses unusual accompaniments, and this piece is scored for flute and cello in addition to guitars, creating a jazzy Arabic sound that is intensified by the singers' plaintive voices. Over and over, the group worked on the complex patterns, until finally, after almost an hour, he called for a break. They sprawled on the floor, resting for the next session.
Noche Flamenca was also rehearsing intensely, in the same simple studio it has rented for years. Decorated with old posters and photographs of great dancers of the past, it seems the perfect place for a troupe dedicated to keeping tradition alive.
But for the first time, Santangelo has given one of his shows a theme. ''After Sept. 11," he said, ''I realized how frightened I and many others were of Muslims and how unhealthy and destructive, and ultimately racist, it was. So I decided to make a piece about fear and the anguish and chaos that fear creates."
He did not have to look far to find songs in flamenco's rich repertoire that described the fear of strangers and its consequences. With his eloquent musicians -- singers Antonio Campos and Manuel Gago and guitarists Jesus Torres and Eugenio Iglesias -- he developed a score that captures all the emotions he hopes ''La Plaza" will convey.
In rehearsal, the troupe alternated dance solos with duets. The electrifying Barrio and the remarkable dancers Isabel Bayon, Juan Ogalla, and Antonio Rodriguez all expressed the music's meaning in their own striking fashion: Barrio with fire and passion, Bayon with sensuality and grace, Ogalla proudly and with elegance, and Rodriguez with barely contained ferocity. Subtle artists, they never resorted to gimmicks or theatrics; they can burn up the stage without them.
As they rehearsed, Santangelo, who also trained in theater, gave his dancers light cues and kept rearranging chairs in the middle of the studio, trying to find the best way to organize the space.
Even as afternoon turned to evening, no one appeared tired or bored. Waiting to repeat her solo, Bayon intently watched the others go through a particularly passionate sequence. ''It's a privilege to dance flamenco as true and honest as this," she said.