RNIE ENSLEY'S spare one-bedroom in a Bronx housing complex for the elderly could hardly be further removed from the Palladium, the glamorous nightclub that presided at Broadway and 53rd Street from the 1940's into the 60's.

But sit on the raggedy futon, close your eyes and open your ears, and everything changes. Mr. Ensley, who turned 70 last week, has amassed in his East Tremont apartment an extraordinary collection of the mambo music that was performed at the Palladium and just about every other important Latin club in New York during mambo's heyday and in the decades since.

The items, which include thousands of audiotapes plus videotapes and other material, fill two closets and line a whole side of the living room, while Latin music posters cover most of the walls. In this shrine to mambo, in fact, about the only hint that Mr. Ensley cares about anything else are the photos of his 26-year-old daughter, Onkeea.

For years, Mr. Ensley has received many inquiries about his collection and, for the last few months, he has been negotiating their transfer to the Raices Latin Music Collection, a 16,000-item archive of Afro-Caribbean music based in the Harbor Conservatory for the Performing Arts in East Harlem. In April, Raices received a grant from the Ford Foundation to obtain and preserve the tapes.

Last week, a longstanding verbal agreement between Mr. Ensley and Raices collapsed over Mr. Ensley's proposed consulting fee. But the negotiations will continue, and the outcome of those talks will be of compelling interest not only to aficionados of mambo and of Latin music in general, but also to music historians. While other collections of live mambo recordings may exist in private hands, musicians and officials at Raices say the Ensley tapes may be unique in their scope.

"As far as live recordings of so many musicians, bands, special events - it doesn't exist," said Ramon Rodriguez, the Conservatory director. "He has a vast knowledge of where, who and what happened with this music, because he was there."

Robert Farris Thompson, a professor of African and Afro-American studies at Yale who hung out at the Palladium in the 50's and has often invited Mr. Ensley to speak to his classes, agrees with this assessment of the collection. Professor Thompson has heard only samples of the collection, but, he said, "The cultural DNA on what he gave me was so strong, it blew me away."

Even the collector himself is impressed with his holdings. "You wouldn't believe the music I have here," said Mr. Ensley, still graced with his dancer's slender build, as he gazed about his apartment one day recently.

Mr. Ensley did not just document the mambo craze: he was a prominent part of it, a fixture at the Palladium as both a dancer and a recorder of live shows, as well as a D.J. at other spots. Even today, Mr. Ensley is a keeper of the flame, still spinning old mambos and pachangas at Orchard Beach on summer Sundays, and working regularly as a D.J. at clubs catering to the older set.

But the modern scene is just a faint echo of the one that flourished in the 50's and 60's, when dance floors shook with the rhythms of that singular musical style, especially in this city. "Mambo was a tale of many cities," Professor Thompson said, "but the richest vein was New York."

Dancing That Made the Ceiling Shake

In the late 1940's, Dámaso Pérez Prado, a Cuban who had moved to Mexico, experimented with combining Afro-Cuban rhythms with the saxophone and trumpet riffs that were a hallmark of big bands. These innovations, on top of others in Cuba in the previous decades, created what came to be known as mambo, a term derived from an African word meaning "conversation with the gods." Mr. Pérez Prado championed a version of the new sound that was popular on the West Coast, but New York was also a mambo capital.

Mambo was an early Latin crossover success, but unlike so many other crossovers, it did not immediately get watered down for consumption by its new broader audience, at least not in New York. But that did not dim its allure. A 1954 article in Life magazine offered its vast readership - the very definition of mainstream America - step-by-step mambo instructions, along with a photo of Oregon schoolchildren learning mambo in gym class.

Some mambo lyrics made this broad interest explicit, such as these lines from "Mambo a la Savoy," by Machito and His Afro-Cuban Orchestra:

Here's the latest dance creation, it's not a fad, the real sensation

Latins can do it, you can do it too.

It was started by a Latin, who brought

the dance to old Manhattan

And he called it Mambo a la Savoy.

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