Istanbul (Turkey)

She fused her mathematical knowledge with minimalist sounds and global spiritual traditions, most notably in her 1976 composition “The Electric Harpsichord.”Catherine Christer Hennix, a Swedish experimental musician and artist who fused minimalist drones, mathematical logic and global spiritual traditions into an approach she called “infinitary composition,” died on Sunday at her home in Istanbul, Turkey. She was 75.The cause was complications of an unspecified illness, according to Lawrence Kumpf, the founder and artistic director of Blank Forms, an organization that has promoted Ms. Hennix’s work. She had previously been treated for cancer.At 20, Ms. Hennix was already a promising mathematician, jazz drummer and electronic composer when she visited New York in 1968 to explore the downtown Manhattan arts scene. She soon met the pioneering minimalist composer La Monte Young and immersed herself in his world of drone music and “just intonation,” an alternative to the standard tuning system of Western music.In 1970, an encounter with the Indian classical singer and guru Pandit Pran Nath, whom Mr. Young had helped introduce to the West, further defined Ms. Hennix’s career and sound. Along with other prominent experimental musicians, including Terry Riley and Jon Hassell, she became a disciple of Mr. Nath, a so-called guruji. She was particularly drawn to the complex, shimmering sound of the raga’s underlying tambura drone, which seemed to stretch on endlessly in time.“You get your first intuitive acquaintance with infinity through the raga, and then mathematics amplifies this concept of infinity by teaching you to formally manipulate it on paper with symbols,” Ms. Hennix told the writer Marcus Boon in 2001.Alongside music making, she wrote poetry, logical equations and Japanese Noh dramas. Her efforts culminated in a 10-day festival called Brouwer’s Lattice, which she curated in 1976 at Moderna Museet in Stockholm and which included presentations of her art installations as well as performances by other minimalist musicians.The festival also featured “The Electric Harpsichord,” a full-scale synthesis of Ms. Hennix’s seemingly divergent interests. Utilizing a Yamaha keyboard calibrated to just intonation, she improvised on a raga scale and fed the results through a tape delay, all atop a constant drone. The result was a strange, trembling and powerfully uncanny soundscape. Though the extant recording of “The Electric Harpsichord,” from its first and only performance, is 25 minutes long, Ms. Hennix envisioned the music to have no end.Minimalist music went mainstream in 1976 — with groundbreaking compositions like Philip Glass’s “Einstein on the Beach” and Steve Reich’s “Music for 18 Musicians” — but Ms. Hennix remained resolutely underground, committed to the ethos of the infinite drone and to a kind of artistry that could not be contained in a traditional concert setting. (The Deontic Miracle, her gagaku-inspired trio, which debuted at the Stockholm exhibition, had rehearsed for four years and never played a second concert.)Ms. Hennix then collaborated with the equally uncompromising artist Henry Flynt on a series of projects they described as “hallucinogenic/ecstatic sound experiences.” In 1979, they presented tapes of their music at the Manhattan performance space The Kitchen, including the recording of “The Electric Harpsichord.” Mr. Flynt heralded it as “unclassifiable and out of this world.” A skeptical New York Times critic, Ken Emerson, wrote that Ms. Hennix’s music “concluded an otherwise fascinating evening on a shrill, buzzing note that rang unpleasantly in this reviewer’s ears.”For decades afterward, Ms. Hennix toiled mostly in obscurity.“My contention has always been that the future of music and art, sound and light, needs aesthetics to coalesce with ethics,” she told Mr. Boon in 2020 in an interview for The Brooklyn Rail. “This has certainly been a hard sell during my 50 years as an active composer, which is why public exposure to my work has been very limited, not to say nonexistent, over long periods of time.”In the 21st century, however, Ms. Hennix’s work has undergone something of a revival. The partial recording of “The Electric Harpsichord” was finally released in 2010, and since 2016 Blank Forms has presented her concerts, released archival and new recordings, and published two volumes of her theoretical writings.She was born on Jan. 25, 1948, in Stockholm, to Gunnar Noak Hennix, a doctor, and Margit Sundin-Hennix, a jazz composer. Inspired by her older brother, she took up the drums at age 5. The flourishing Swedish jazz scene brought many American luminaries to Stockholm, and as a teenager she was transformed by hearing the saxophonist John Coltrane live.Ms. Hennix studied linguistics at Stockholm University and later pursued graduate studies in mathematical logic, drawn to the theories of Fourier and Brouwer. At Stockholm’s electronic music studio, she created synthesized compositions in the style of Karlheinz Stockhausen, but ultimately concluded that the hyper-complexity of European modernism was a dead end.Instead, it was Mr. Young’s drones that seemed to offer a path forward. The first time she heard his music, she recalled in 2010, “it took me about 60 seconds to decide that this was the sound.”Through the 1980s and ’90s, Ms. Hennix undertook other projects, including drumming in a band with Mr. Flynt called the Dharma Warriors; teaching logic and mathematics at the Massachusetts Institute of Technology’s Artificial Intelligence Laboratory and at the State University of New York at New Paltz; and working with the Soviet-era dissident mathematician Alexander Esenin-Volpin.She moved back to Sweden and then to Amsterdam, where she collaborated with the photographer Lena Tuzzolino, her partner for about a decade. She eventually moved to Berlin, though she never found an artistic scene that fully supported her quixotic worldview.Ms. Hennix had been introduced to Sufism during her formative discipleship with Mr. Nath. In recent years, she converted to Islam, studying classical Arabic and the Turkish style of maqam music. In 2019, she moved to Istanbul, in part to regularly hear the call to prayer.Ms. Hennix, who had gone by Christer, began identifying as a woman in the late 1980s, and became known as Catherine or C.C. No immediate family members survive her.“Her refusal to be consumed by the practical conditions that most of us are consumed by really opened up this profound inner experience and inner exploration for her that in many ways didn’t need an audience,” said Mr. Kumpf, the Blank Forms artistic director. “It’s a spiritual practice: It’s between her and no one else.” More