Sunjae Lee (이선재) is a saxophonist, composer and free improviser who was born in Boston, Massachusetts, and has lived and worked in Seoul since 2014. He is also the founder of the Seoul label Mung Music, which since 2020 has issued records by a wide circle of Korean improvisers. No source gives his birth date or his citizenship. The American listing site Jazz Is Discovery calls him a Korean-American, and his releases and press coverage place his working life in Korea, where he has lived for twelve years.

His own biography on the website of the mouthpiece maker Syos says he began music on piano, violin and saxophone at Rivers Music School in Boston and went on to the New England Conservatory's preparatory program. He then studied chemistry at the University of Rochester and upright bass at the nearby Eastman School of Music. The trumpeter Peter Evans, who plays on his later album Entropy, is described in Lee's own release notes as a longtime collaborator from his Boston upbringing, and The Free Jazz Collective's reviewer calls the two classmates at the conservatory's preparatory school.

Back in Boston he made three albums for the label Pure Potentiality between 2007 and 2009. Srivbanacore (2007) is a set for alto saxophone with the pianist Ben Stepner, the drummer Dan Nadeau and the trumpeter Phil Grenadier. Meditations (2008) is a solo record of saxophone, flute and electronics, and Equilibrium (2009) a solo record of soprano and tenor saxophone with electronics, two of its three pieces running past twenty minutes. Discogs notes that the last two first appeared under the name Eugene Lee, and both carry liner notes by Jeff Dayton-Johnson.

Music then took second place. In early 2010 he moved to Portland, Oregon, to study natural medicine, and by the Syos biography he earned a doctorate in naturopathy and Oriental medicine there; Jazz Is Discovery says he spent six years in the city. He kept playing. His Portland group, the Kin Trio, with the bassist Andre St. James and the drummer Tim DuRoche, recorded the live-to-two-track album Breathe at Tango Berretin on January 28, 2013 and released it on PJCE Records, and the trio played the PDX Jazz Festival.

In the interview he gave PAN M 360 in 2020, Lee said he cared little about his Korean heritage while growing up in Boston. The change came in Portland, where learning about Korean traditional medicine and taking up Asian brush painting pulled him toward Korean ancestry and language. He moved to Seoul in 2014 to practice naturopathy, and he has stayed: Bandcamp lists his location as Seoul, South Korea, and the notes to Entropy describe it as his first studio album since moving to Korea. He still practices medicine and paints in the Oriental brush tradition, and he designs the covers of the records on his own label.

Once in Seoul he found his way into the city's improvising community. By PAN M 360 he played in the drummer Soojin Suh's Chordless Quartet, and he is credited on tenor and soprano saxophone on Suh's album Strange Liberation (Mirrorball Music, 2018), with Daniel Ko on alto, Hoo Kim on bass and Suh on drums. His own trio of the period, billed Trio Go, with the guitarist Jinwon O and the drummer Junyoung Song, improvised the six pieces of Sounds Much Better at the Yogiga Expression Gallery in Seoul in 2015; the record was mastered in Seoul in 2016 and appeared in 2017 on Dancing Butterfly Records as a vinyl edition of 300 copies. His Syos biography says that in 2016 his trio won the Grand Prize and the Best Creativity Prize at the Jarasum International Jazz Festival Concours.

Entropy, released on January 15, 2019, was his first studio album since moving to Korea. Recorded at Yireh Music Studios in Seoul and mixed and mastered by the bassist Eivind Opsvik, it pairs Lee on alto and soprano saxophones with Evans, the bassist Minki Cho and Song, and with the vibraphonist Chris Varga on two tracks. Lee wrote most of the music as guided improvisation or around indeterminate elements: "Alternative Facts" fixes the rhythm of a thirty-two bar form but leaves the pitches open, and the title piece has each player follow a diagrammatic chart that resembles a board game. "Daedalus" and "Icarus" are two duo improvisations with Evans, the first tracks laid down that day. Derek Stone reviewed it for The Free Jazz Collective on January 10, 2019, praising a player who moves between flowing lines and fragmented outbursts, and Jazz Trail's flash review also heard a raw, spiky record.

In October 2019 he played saxophone on three tracks of 이상한 꽃 ("Strange Flower", Mirrorball Music), the vocalist Jimin Lee's settings of poems by Yi Sang, alongside the pianist Eunyoung Kim and Song. The year 2020 was a turning point. Channel (April 1, 2020), seven solo saxophone improvisations on tenor, alto and soprano recorded over a week in December 2019 at the Seoul venue Ghetto Alive, was his first album given wholly to solo improvisation. On January 15, 2020 he, Eunyoung Kim and the drummer Dayeon Seok recorded the single 50-minute improvisation Pulse Theory at GhettoAlive, issued on GhettoAlive Records and mastered by Opsvik. On July 1 he recorded Palindrome at the Seoul studio BOOMiz with the trumpeter Choi Sun Bae and Song, direct to a Tascam 424 cassette recorder, and issued it on his new label. In his PAN M 360 interview Lee named Choi as an important elder of the scene who supports younger players. He recorded the duo album Claustrophobia with Song on December 10, 2020 at Stradeum in Seoul on the same cassette machine; it came out in 2021, and The Free Jazz Collective's Keith Prosk heard calm yet stirring inside-outside compositions with the mood of early to mid-1960s Blue Note records.

Mung Music is the larger part of his public work. The name comes from the Korean word 멍, roughly "spacing out", which Lee ties to the way improvisation lets the subconscious take over. The label's own description says it focuses on improvised and original music from Seoul, mainly recorded on a vintage Tascam 424 cassette four-track, with all artwork by Lee. Its first batch, in the summer of 2020, was Earworm by Eunyoung Kim, Saaamkiiim's Ma-chal, Baum Sae's Embrace and Palindrome. Discogs lists twenty releases between 2020 and 2025, among them Jeremy Noller's Passage (on which Lee plays saxophone on two tracks), Daniel Ko and Soojin Suh's Alchemy, the bassist Michael Bisio's Inimitable, which Lee executive-produced, Chris Varga's Vichara and the 2025 live compilation Galpi from the MOIM improvisation gatherings. Lee recorded, mixed or mastered many of them himself. He told PAN M 360 that he works full time in medicine, that the label is not about profit, and that he hoped international attention would help the musicians secure grants and be paid fairly. His Discogs biography adds that he operates Seoul Experimental, a community calendar of experimental and improvised events in the city. He described the Seoul free-improvisation world as small and nearly underground, with pockets of musicians he was trying to join together; he named Choi Sun Bae as an important elder, the saxophonist Kang Tae Hwan as respected but reclusive, and Alfred 23 Harth, who has lived in Korea for about twenty years, as someone who had also begun playing with the group.

His recent playing has leaned further toward the experimental edge. Shamanism, a quartet record by the saxophonist Jung-Jae Kim, with Lee on soprano and alto and the drummers Junyoung Song and Sunki Kim, was recorded at Tune-Up Studio in Seoul on August 14, 2023 and released by Relative Pitch Records on June 20, 2025; its twelve pieces are named after Korean ideograms and follow the stages of a shamanic ceremony. In 2025 he appeared on the cassette Wafer Thin / Wide-scale and Indiscriminate Seizure (Ethnicity Against The Error), its second side credits Kikanju Baku on drums and samples, Lee on tenor saxophone and Dayoon Lee on noise. Mirror Dimensions, a vinyl LP from the same label released on April 29, 2026, pairs Baku with Lee on tenor saxophone on one side, recorded live at DIP Industries in Seoul on September 7, 2024, and with the alto saxophonist Chris Pitsiokos on the other, recorded four days later.

His Discogs biography describes music that joins compositionally structured forms rooted in jazz to free improvisation and extended techniques, and the site files his releases under Avant-garde Jazz, Free Jazz and Free Improvisation. A description of Srivbanacore there hears three pieces in the lower range of the alto, played freely but with one foot in the tradition, and three minimalist pieces in its higher register; the two solo albums that followed move toward long improvisations with electronics. In Seoul the writing turned toward compositions that hand decisions to the players: chosen-pitch melodies, cue-based solo sections and diagrammatic charts on Entropy, and fully improvised sets on Channel, Pulse Theory and the Mung Music sessions.

Critics have reached for several reference points, none of them influences Lee has named. The Free Jazz Collective heard echoes of classic free jazz in Entropy, compared "Foxdeer" to the small-group music of Anthony Braxton in the mid-1970s, and described a saxophonist who builds circular repeating figures, wails on the soprano and treats the horn as an extension of his body. Jazz Trail heard Ornette Coleman, Charlie Parker and Dave Liebman in the same record. For Claustrophobia the Collective's reviewer called the music largely melodic, the pieces catchy enough to be earworms. His own notes explain that the closing "Body" is an alternate melody over "Body and Soul" and that "World on Fire" was written while forest fires burned in the Columbia River Gorge in Oregon, a place he loved during his years in Portland.