Question:  Sigur Rós' EP consists of the songs the group composed for an American dancer and choreographer who was at the forefront of the American modern dance for more than how many years?

Context paragraphs:
Eleanor King: Eleanor Campbell King (1906–1991) was an American modern dancer, choreographer, and educator.  She was a member of the original Humphrey-Weidman company, where she was a principal dancer in the pioneering modern dance movement in New York City, then moving on to choreography and founding her own dance company in Seattle, Washington.  She was a professor emerita at the University of Arkansas, where she taught from 1952 to 1971, before retiring to Santa Fe, New Mexico to start a new course of study into classical Japanese and Korean dance.  She choreographed over 120 dance works, and wrote extensively for a variety of dance publications.  In 1948, she was named Woman of the Year in Seattle, and in 1986 was listed as a "Santa Fe Living Treasure", also receiving the New Mexico Governor's Artist Award.  In 2000, her archive was recognized by the White House Millennium Council's "Save America's Treasures" program.

Contemporary dance in Japan: Western schools covered classical ballet, jazz-dance, and modern dance and influenced the butoh avant-garde dance movement.  Ballet was said to have replaced traditional Japanese arts, such as flower arrangement and the tea ceremony, in the hearts of young girls.  Prima ballerina Morishita Yoko sat on the jury for the Prix de Lausanne Ballet Competition in 1989, held for the first time in Tokyo, marking the arrival of Japanese classical ballet in the international community.  Horiuchi Gen, a 1980 Prix de Lausanne winner, became a major soloist with the New York City Ballet, and Japanese performers noted for their superb technique were members of many major international companies.  Modern dance was performed early after World War II and was later taught by such famous dancers as Eguchi Takaya.  The Tokyo Modern Dance School and the Ozawa Hisako Modern Dance Company also promoted avant-garde modern dance.  A wide experimental range within modern dance occurred from which choreographer Teshigawara Saburo skillfully drew to create multifaceted works for his KARAS Company.

Graham technique: Graham technique is a modern dance movement style and pedagogy created by American dancer and choreographer Martha Graham (1894–1991).  Graham technique has been called the "cornerstone" of American modern dance, and has been taught worldwide.  It is widely regarded as the first codified modern dance technique, and strongly influenced the later techniques of Merce Cunningham, Lester Horton, and Paul Taylor.

Kjartan Sveinsson: Kjartan "Kjarri" Sveinsson (] ; born 2 January 1978) is former keyboardist for the Icelandic post-rock band Sigur Rós.  He joined the band in 1998.  A multi-instrumentalist, he has also played such instruments as the flute, tin whistle, oboe, guitar and even the banjo, as well as many of the unorthodox instruments that contribute to Sigur Rós's distinctive sound.

Merce Cunningham: Mercier Philip "Merce" Cunningham (April 16, 1919 – July 26, 2009) was an American dancer and choreographer who was at the forefront of the American modern dance for more than 50 years.  He is also notable for his frequent collaborations with artists of other disciplines, including musicians John Cage and David Tudor, and artists Robert Rauschenberg and Bruce Nauman.  Works that he produced with these artists had a profound impact on avant-garde art beyond the world of dance.

Sigur Rós discography: The discography of Sigur Rós, an Icelandic post-rock group, consists of seven studio albums, one remix album, three extended plays, one soundtrack album, fourteen singles, nine music videos and two video albums.  Sigur Rós was formed in 1994 in Reykjavík, Iceland, by singer and guitarist Jón Þór Birgisson, bassist Georg Hólm and drummer Ágúst Ævar Gunnarsson.

Ze'eva Cohen: Ze'eva Cohen is a dancer, modern dance choreographer, and dance professor emeritus at Princeton University.  Cohen grew up in Tel Aviv, Israel, the daughter of Yemeni immigrants.  She traveled to New York City from Israel in 1963 to study at the Juilliard School and perform with the Anna Sokolow Dance Company.  She danced with the company for ten years.  Cohen was also a founding member of Dance Theater Workshop, where she worked as a choreographer and dancer from the mid-sixties to the early seventies.  She has created a body of choreographic work which links her background in American modern dance with her Yemenite Jewish heritage.

Lila York: Lila York (born 29 November 1948) is an American dancer and choreographer based in New York City.  She studied English Literature at Skidmore College before studying ballet and modern dance at the Martha Graham Center of Contemporary Dance and with Paul Sanasardo.  York joined the Paul Taylor Dance Company in 1973 where she danced for more than a decade.  After leaving the company, she left the "very heart of American modern dance" to become one of "ballet's most sought-after choreographers", working with many of the world's foremost ballet companies.

Ba Ba Ti Ki Di Do: Ba Ba Ti Ki Di Do is an EP by Sigur Rós, released in 2004 by Geffen Records.  The EP consists of the songs the group composed for Merce Cunningham's dance piece "Split Sides", which also involved Radiohead.

Sarah Swenson: Sarah Swenson is an American modern dance choreographer, dancer, and teacher.  She trained in early modern dance forms, and later studied postmodern dance.  She began her career in the 1990s in New York City, where she held numerous positions in the field.  Swenson began as a teacher at the Alvin Ailey School, and was Rehearsal Director and Performance Coach for the Alvin Ailey Student Performance Group, for which she created her first works.  She was also the Associate Artistic Director of Seraphim Dance Theatre, founded by the late Raymond C. Harris.

Supporting paragraphs: Ba Ba Ti Ki Di Do Merce Cunningham
Answer: 50