So what else was Conlon Nancarrow, a native of Texarkana, Arkansas, to do but move to Mexico, give up his U.S. citizenship and write music mostly for the player piano, of all the instruments under the sun, that is now considered to be among the most influential produced in the 20th century?

Nancarrow, who died in 1997, often is described as "the greatest composer you've never heard of", but for Rex Lawson, who will be in charge of live performances of Nancarrow's player piano works at a weekend-long festival at London's Southbank Centre April 21-22, he is nothing less than a modern Bach.

"I've always felt in a sense that Bach is the center of the universe...and you get that sort of feeling with Conlon, mixed in with excitement and wit," Lawson, who is a specialist in player pianos and knew Nancarrow, told Reuters in an interview.

"Almost all his pieces have at the end something that makes an audience smile, a kind of sideways twinkle of the eye -- and he was like that."

Southbank is taking a gamble putting on a weekend of music and art celebrating the works of a composer so little known to the general public.

Organizers are hoping the wit, as well as the genius, of this iconoclast who joined the American Communist Party in the 1930s, fought with the Abraham Lincoln Brigade to defend the Spanish republic, and felt the chill wind of anti-communism when he made it home alive, will shine through.

"My real aim for this is it should be entertaining," said Dominic Murcott, head of music composition at Trinity Laban Conservatory of Music and Dance, which is a partner in the weekend's activities, along with the London Sinfonietta.

"It might take a little bit of work, but I hope it will put a smile on your face."

Although Nancarrow did write "ragtime that's totally bionic" as Zappa, who became a composer himself after he moved on from the seminal Mothers of Invention 1960s rock band, put it, his real specialty was testing the boundaries of time. One of his studies for player piano consists of no fewer than 12 melodic lines, each progressing at a different tempo.

"FISTFULS OF NOTES"

Much of his music can be described as sounding like "fistfuls of notes" moving along at such tremendous speed that no human pianist could ever hope to play it -- hence the player piano.

The one that will be gracing the small, 380-seat Purcell Room of the Queen Elizabeth Hall is, Southbank says in its publicity material, "an original Ampico reproducing piano identical to the composer's own".

Lawson, who will be at the controls, is thrilled the programs might lead the audience to think that he and Wolfgang Heisig, a German Nancarrow devotee, will be playing the Ampico, when, he admits, "We don't do anything -- all we do is switch the piano on."

The piano, and the paper rolls filled with slits that Nancarrow used to painstakingly cut out, but now can be produced by computer technology, do the rest, but that does not mean Lawson and Heisig are off the hook. They will be saying a bit about the music while the rolls are being rewound and changed, which is something Murcott thinks is essential.

"I think for better or worse, Nancarrow needs a map to really enjoy...It's like a piece of conceptual art. No one really creates a piece of conceptual art without a kind of thesis that goes with it," Murcott said.

"So this will be trying to welcome people into this guy's world."

In addition to the 50-odd studies and other pieces Nancarrow created for the player piano, the weekend will feature the London Sinfonietta in a program of his large-scale works.

The Arditti String Quartet, for whom the composer wrote his String Quartet No. 3, will play all of the quartets, a player piano study arranged for quartet and the String Quartet No. 2 by the Hungarian modernist Gyorgy Ligeti, a big Nancarrow admirer.

To enhance the mood, the Queen Elizabeth Hall will be the setting for the first British display of German-born sound installation artist Trimpin's "Conloninpurple", described as consisting of "10 hanging chains of fuchsia-colored trumpets" and having an acoustic range of five octaves.

Hearing will be believing, which is exactly what Southbank wants.

"We are thrilled to be hosting the first UK celebration of one of the most innovative composers of the 20th century," Gillian Moore, head of classical music at Southbank, said.

"For those not familiar with Nancarrow's music, this immersive live experience is the perfect opportunity to understand where so much avant-garde contemporary music comes from."

(Editing by Paul Casciato)

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