Kim Hyun Il (김현일) is a tenor saxophonist from Seoul who has worked in Korean clubs, big bands, musical-theater pits and recording studios since about 2000, and who leads two bands of his own: a quartet and the nine-piece swing band Maeil Nonet (매일 노넷). The biography on his Bugs artist page gives his birth date as December 17, 1976, in Seoul, lists tenor and soprano saxophone, and says he graduated from the jazz department of Jaeneung College in Incheon and then completed the jazz instrumental course at a school in Amsterdam; the Korean word it uses means finishing the coursework, not taking a degree, and no years are given for either school. A club-schedule biography posted in March 2011 repeats the same facts almost line for line and calls the Amsterdam school a conservatory. He is 49.

The first dated trace of him in the press is a notice in the Maeil Shinmun of Daegu on August 18, 2004, for a concert on August 21 at the Indigo jazz cafe by the quartet of the alto saxophonist Hong Soon Dal, with Kim on tenor, Choi Dong-ha (최동하) on drums, Sung Gi-moon (성기문) on piano and Jo Seong-deok (조성덕) on bass. The notice describes Kim as a member of the Latin jazz band Cobana (코바나). A 2008 liner note names the pianist Yang Joon-ho as music director of a Latin jazz group of that name, though no source connects the two directly. Pressian's concert notice of March 2011 adds that his earlier work included an army band in 1998, musical sessions, a Latin big band, pop singers and broadcast work, and the notes of the 2007 album Day Break say he had worked in musicals, pop sessions and club shows since 2000. His own biography lists concerts and sessions for the harmonica player Jeon Je-deok, the singers Yoon Hyung-joo, Yoo Yeol, Park Jung-hyun, Alex and Lee Seung-hwan and the idol Kang Ta, a trip to Beijing with Shin Kwan-woong's big band, the musicals Sex Is Zero (색즉시공) and All That Jazz, a performance with the National Dance Company, and television and radio spots on KBS, EBS Space Gonggam, SBS and MBC. None of those items carries a date.

His first recording under a band name that can be dated is the 2007 quartet Portrait (포트레이트). The drummer Lee Chang-hoon (이창훈), who had studied jazz drums and vibraphone at a conservatory in the Netherlands, formed it in 2006 with Kim on tenor, the pianist Yun Seokcheol, then in his early twenties, and the bassist Lim Dae-seop (임대섭). The album notes say Kim proposed the name. The debut, Day Break, came out on May 18, 2007: ten tracks and about 63 minutes, with the singer Soyoung Heo as guest on four vocal tracks and as lyricist. It mixes standards ("The Song Is You", "I Thought About You", "Spring Is Here"), Jobim's "No More Blues", two pieces tied to Thelonious Monk and Yun's three originals, and its title track on Bugs is "연인" (Lovers). The notes say Kim and Lim also played together in a group called Lush Life, to which Yun belonged as well, and that Kim had a quartet under his own name by then.

Alongside the quartet he played tenor for eight years in the Jazzpark Big Band (재즈파크 빅밴드), according to the notes of 2015. The band released a single in 2008, a Christmas album in December 2009 and Jazzic in 2011; his own biography and the notes of his first solo album say he appears on its first album and Christmas album, and on Lee Han-jin's first album, a musical-theater recording of All That Jazz and the third Ginagram album, but the Bugs pages for the band's records and for Ginagram do not itemize players, so those appearances rest on his account. In August 2012 the Dream Square Jazz Park Club in Cheongdam-dong, Seoul announced resident performances from August 30 by the big band and several groups, among them the Kim Hyun Il Quartet.

Memory, his first album under his own name, was released on August 13, 2010. It is seven tracks and about 48 minutes, and the notes say he wrote every piece. The title track "Boracay" is Latin jazz; "Kiwi" is a blues he took from the black seeds of a kiwi fruit, with a piano technique the notes single out; "The Memory of Old Days" looks back to childhood. The notes do not name the players. In March 2011 he took part in a ten-day series of Korean jazz concerts presented by the critic Hwang Deok-ho at the Munhwa Ilbo Hall in Seoul, closing it on March 31 with the Kim Hyun Il and Sung Gi-moon trio, which the papers called the country's only saxophone and organ trio, with the guitarist Kang Woong; a Seoul club listed the same pairing at Jazz Alley on April 1, with the guitarist Park Yoon-woo and the drummer Kim Hak-in.

In mid-2014 he started Maeil Nonet, a nine-piece band that keeps the core of a big band: a rhythm section, two trumpets, two trombones and an alto saxophone besides his tenor. The label's notes say that he had been pursuing orthodox hard bop and then turned to jazz with wider appeal. Playground of Maeil Nonet (매일 노넷의 놀이터) came out on May 11, 2015 with guest singers Go A-ra (고아라) and Lee Yu-cheol (이유철) and the percussionist Choi Geon; he is credited with the music, the arrangements and the Korean words. Bugs named it its album of the month for June 2015, and the band played the Jarasum International Jazz Festival that autumn, with video recordings of the set posted on October 25, 2015 by a channel in the bassist's name. The second album, A New Lie, arrived in 2017 as two EPs, A New Lie Part.1 (February 23) and Part.2 (March 3), and then as the seven-track album on March 9, with the vocalist Yoon Deok-hyun (윤덕현) added; he again wrote all the music and words.

His later dated appearances are scattered. On May 15, 2021 his band Band Six (밴드식스) was announced for a classical-jazz program with spoken commentary by Kim at Lara Hall in Seocho, Seoul, with tunes including "Song for My Father" and "To Sir with Love". On June 16, 2021 his quartet played at Jeonbuk Bank's JB Culture Space in a talk-and-concert series with Hwang Deok-ho. As the tenor saxophonist of the Lush Life Jazz Band, a dixieland, swing and Latin sextet with the trombonist Lee Han-jin that the press said had been active for twenty years, he was listed for Bottomline in Incheon on May 18 and October 19, 2024. In March 2025 a channel about Kim Kwang-seok Street posted a full set by the Kim Hyun Il Quartet with the singer Yoohara (유하라) at a venue called Nabal Acoustic, and in May 2025 the Itaewon club All That Jazz in Seoul posted two quartet pieces. On August 13, 2025 he released the two-track single Dawn over the East Sea (동해에 해가 뜨면), a bossa nova inspired by Getz/Gilberto with Yoohara's words, paired with a jazz-funk setting of the folk songs "Doraji Taryeong" and "Baetnorae" by the quartet.

He is not the K-pop singer and songwriter Kim Hyun-il of C-Clown, nor the singer of the 2011 album Man Like an Angel (천사표같은 남자), whose records sit under the same name on the streaming services; none of their credits is his. No Wikipedia article, Wikidata item, Discogs entry or MusicBrainz entry exists for him, no interview with him has turned up, and the full list of his session and studio work is not published.

Everything in the notes to his own records points to a mainstream saxophonist who likes melody: the release notes for Memory describe the lyrical, deeply felt tone of a player writing from memory, the Day Break notes group him with musicians pursuing swinging hard bop, and in 2015 he described himself as having begun with orthodox hard bop before turning to more popular jazz. Maeil Nonet is the result. The notes call its music swing from the 1930s and 1940s with Latin and contemporary touches, sung in Korean over a horn section, and they name the sources behind individual pieces: Louis Prima for "썸 & Love", a Blossom Dearie tune for "Tic Tic", Duke Ellington's Concerto for Cootie for "Lazy Afternoon" and Ray Charles for "Don't Forget"; "Time 2 Blues" is described as New Orleans style and "Midnight Sunset" as a minor-key Latin piece.

The 2025 single widens that. "Dawn over the East Sea" came from listening to Stan Getz and Joao Gilberto's album, and the second piece moves the semachi and gutgeori rhythms of traditional Korean music into 4/4 jazz-funk. Bugs files Memory as jazz, the Portrait album as contemporary jazz and the Maeil Nonet albums under swing and big band, while Apple Music lists Playground as easy listening.