SE:UM (세움), also written SEUM and billed on its recent releases as Music Group SE:UM (뮤직그룹 세움), is a South Korean quintet that sets a jazz front line and bass beside the gayageum, the twelve-string Korean zither, and Korean percussion. Joon Lee (이준) plays gayageum and is the music director and producer. He is joined by Hachul Song (송하철) on alto and soprano saxophones, Jongsang Park (박종상) on trumpet and flugelhorn, Jaeha Lee (이재하) on double bass and electric bass, and Minhyung Lee (이민형) on janggu, the hourglass drum, with voice and other percussion. The group describes itself as two players of Korean music and three players of Western music, whose backgrounds run through gugak (Korean traditional music), jazz and pop.

The debut album's own text dates the group to September 2013, and two North American presenters describe the start as jam sessions between jazz players and Korean traditional musicians working from folk melodies and shamanistic rhythms. A 2016 news article counts five years since the group's founding, which would point to 2011, so the founding year is stated here as 2013 with that discrepancy noted. In a 2024 interview Lee said the early rehearsals were hard because jazz and Korean traditional music communicate differently, and that the band grew more harmonious over time. The debut's text names a different music director, Kim Seong-bae (김성배); his later role is not documented, and the 2022 piece "Requiem" is credited to Joon Lee and Kim Sungwan (김성완) together.

The self-titled debut, SE:UM, came out on November 18, 2014 with nine tracks, among them "Seven Steps One Bow" (칠보일배), the title track "I-Eo-Do" (이어도), "Abyss" (심연), "Sa-Gye-Hwa" (사계화), "Smell of the Water" (물내) and "The Big Parade" (대열병). Its text calls the music a Korean form of trance music that joins Korean rhythmic cycles to Western free music and jazz, and says the group had been engaged for the Seoul Art Market's tenth-anniversary performance in 2014. Presenters' biographies and the Korea Arts Management Service say the album was nominated in two categories at the 2015 Korean Music Awards, Best Crossover Album and Best Jazz & Crossover Performance; the awards covered releases from December 2013 to November 2014, which fits the November 2014 release date, and the winners in both fields were other artists. Melon files the album under gugak and crossover.

In 2015 the group's stage show Korean Breath, a mix of improvised jazz and Korean traditional music built around the idea of breath as a musical element, was chosen as a PAMS Choice work at the Seoul Art Market. It played the Edinburgh Fringe at C venues from August 16 to 22, 2015, and Broadway Baby's Lydia Nowak gave it five stars on August 20, calling the artistry of the instruments astounding and saying the gayageum is what makes the music stand out. She added that the group's CDs were hard to find online. In 2016 a news article reported an invitation to a Washington, D.C. jazz festival, and the group played the Motor House in Baltimore on July 27, 2016 with the saxophonist Craig Alston's ensemble, a free concert presented by the Korean Cultural Center in Washington that gave US premieres of "Abyss", "The Other Side", "Smell of the Water", "Seven Steps One Bow" and "Sa-Gye-Hwa". That autumn the group was a resident ensemble of the Bupyeong Art Center in Incheon and gave a full-length Korean Breath concert there on October 8, 2016; the same article lists the Jarasum International Jazz Festival, the Ulsan World Music Festival, a Korean festival in Abu Dhabi and an invitation from the Korean Cultural Centre in Nigeria among its earlier engagements. Its last international tour before the pandemic, Lee said in 2024, was the Penang Island Jazz Festival in Malaysia in 2017.

The recorded catalogue then moves to the 2020s. Korean Breath: 만파 (萬波, "ten thousand waves"), released on February 21, 2022 with eight tracks, was made during the pandemic and takes its idea from the Silla-era legend of the flute Manpasikjeok, whose sound was said to settle all of the kingdom's troubles; nine days before release the group played "Seven" and "Manpa" on the KBS television programme Gugak Hanmadang, broadcast on February 12, 2022. A live single of "Requiem" (진혼) followed on November 18, 2022, the first result of the group's work with YAGI Studio, recorded live in one room; the piece begins and ends with a funeral-bier song from the Simcheong shamanic ritual and builds to a percussion solo on Gyeonggi-province ritual rhythms. The Sense of Water (물의 감각), on December 22, 2023, is built around water, and Cycle (순환), on April 30, 2024, is a live album that adds the string ensemble Sigansori (앙상블 시간의 소리) to four of its nine pieces, with arrangements by Eom Ki-hwan and Lee Hyun-jin. Those four, "West," "Nanani," "Origin" and "Circle," are string-ensemble versions of tracks from The Sense of Water.

In spring 2024 the group toured North America as one of the grantees of the Mid Atlantic Arts Performing Arts Global Exchange, with listed hosts including Creative Alliance in Baltimore, Flushing Town Hall in New York, Freight & Salvage in Berkeley, Lehman College in the Bronx, Pro-Art Association in Wise, Virginia, San Jose Jazz Fest and the Vashon Center for the Arts in Washington State. Flushing Town Hall presented it on May 11, 2024 and the Vashon Center on May 1. The Korean Cultural Center New York's page for the Flushing date credits Joon Lee with the 2023 KBS Korean Traditional Music Award for gayageum playing. No album after Cycle is listed on Apple Music, Bugs or Melon.

The sound rests on the gayageum. Joon Lee has described the technique of nonghyeon, a bending and shaking of the string he likens to vibrato but with more in it, as the way emotion reaches the listener, and he says each member's own style comes before any genre label, with the Korean roots and the traditional instruments, the gayageum and janggu above all, as what sets the band apart. His player credits show how far the instrument list stretches: steel-string and bass gayageum, the small gong kwaenggwari, East Coast-style janggu, the taepyeongso (a conical Korean oboe), jing, jeongju, cymbal and ocean drum, with electric bass and flugelhorn on the Western side. The pieces draw on shamanic ritual music, folk song and dance rhythms, and the albums' notes set them under titles about breath, water and cycles of nature.

The scope question is real, and the sources disagree. Melon and Bugs file the albums under gugak and crossover, Bugs tags Korean Breath: 만파 as new age, Apple Music lists the albums under Korean classical, and the Korean Music Awards nominations are in the jazz-and-crossover field, in its crossover and performance categories, not in its jazz album category. The leader and principal voice is a gayageum player, and its 2024 tour was billed "Korean folk meets jazz." Against that, three of the five members play jazz instruments and come from jazz, All About Jazz carries the group, the Edinburgh review and North American presenters frame it as jazz, and it has played jazz festivals in Korea, Malaysia and the United States. This profile treats it as a jazz and gugak crossover group rather than a straight jazz band.