Jamba OJ (잠바OJ) is a South Korean male jazz vocalist, songwriter and producer who teaches practical music at Yeoju University. His real name is 오재이, and the stage name combines a childhood nickname with initials: in a December 2023 interview with OhmyNews he said Jamba is what his family called him as a child, and that OJ is his given name written in Latin letters, added when a manager pushed him to change his early billing of "Jamba" alone. Korean Wikipedia gives his birth date as September 18, 1975, and Wikidata repeats it; no source found names his birthplace. Melon lists his nationality as Korean, his career has been spent in Korea apart from stays in Australia and France, and the press that covers him is Korean.

He started as a pop singer. Korean Wikipedia says he signed with the agency GM Planning in 1998, and he told OhmyNews that he began as a rock-ballad singer. The same interview explains the gap before jazz: hurt by the business, he stopped singing and went to Australia in 2001 on a working-holiday visa, where he worked at a winery and studied wine until 2003. Back in Korea he worked in a wine-related job, learned vocals in a jazz circle he joined as a hobby, and began to get invitations to perform. In 2005, according to Korean Wikipedia, he turned to jazz singing in earnest. The winery stay therefore fits the 1998 debut: it sits in the years after he left pop and before he returned to music.

His first album, The Story of J, came out on September 29, 2009. The release notes on Melon present it as the first full-length album by a male jazz vocalist in Korea. Its ten tracks combine standards such as "All the Things You Are" with his own songs, and the notes list haegeum, accordion, trumpet and cello among the instruments used to color the arrangements. "In the Meantime," which he says was the first song he wrote, is the one he is fondest of, and he re-recorded it for his 2019 album. One track, "Reminiscence," is noted on Melon as an insert song of the TV drama 맞짱. In January 2010 he sang the swing-style "Who Am I" on a commemorative compilation for the city of Incheon, alongside the singer Insooni and others.

The second album, Competition, followed on April 8, 2011. It pairs his originals with jazz readings of "Time After Time," "Misty" and "Smoke Gets in Your Eyes," and with a remake of the late Yoo Jae-ha's ballad "Because I Love You," which the release notes single out. After it, Korean Wikipedia says, he went to France and worked with the guitarist Eric Leboucher-Radiguet. Their EP Le Duo (three tracks, February 28, 2013) was recorded and finished in France, according to the Melon notes, in a deliberately plain acoustic mix with the voice and guitar placed left and right.

By November 2013 he had settled in Busan, where the Busan Ilbo described him as the leader and vocalist of a local jazz group called Chico Cubo (치코쿠보), a performer who had appeared at festivals in Busan, France, Japan and Seoul, and an adjunct instructor in practical music at Dongju College. The paper announced a "No Generation" concert at the Busan Arts Center on November 27, 2013, pairing him with the veteran singer Kim Jun, with Chico Cubo as the backing band. Korean Wikipedia lists a Chico Cubo mini-album for 2013, but no store listing for it turned up. A single, "Veiled," on a digital release titled Purple Moon (August 6, 2013), was issued ahead of a film so that the song existed before the movie did; the film's director rewrote the lyric to fit the story.

In 2016 he published a book on groove singing, 그루브 보컬의 완성. In 2017 the Ulsan Maeil previewed his six-piece group Jamba & Friends for that year's Taehwagang Jazz Festival, with 오창민 (O Changmin) on guitar, 허여정 (Heo Yeojeong) on drums, 윤성희 (Yun Seonghui) on piano, 이검 (I Geom) on bass and 박승준 (Bak Seungjun) on saxophone. By his own count in 2019 he had been a regular radio guest for seven years, on Busan's TBN, on BeFM and on KBS Ulsan, and the 2019 album notes and press say he taught at Daedong University and Dongju College in Busan; a January 2020 article adds that he had founded a vocal crew called VASC.

Shame on You (December 16, 2019) is his third full-length, issued eight years after Competition on the Yul Record label (율레코드). He said the first song was written in 2015, that one producer's deal collapsed in 2017, and that an investor finally made the recording possible. All eight songs are in English. The band is Yun Seonghui on piano, 임대섭 (Im Daeseop) on bass and 유헌석 (Yu Heonseok) on drums, with 안우성 (An Useong) on trumpet for two tracks, the Canadian rapper Chad Corea on the title song and the singer 황수민 (Hwang Sumin) on "Hymn to Freedom." The songs carry social messages. The title track, which comes in a clean and an original version, he says he wrote in anger that the Japanese government has not properly apologized to surviving forced-labor and wartime sexual-slavery victims; other songs refer to the 2016 candlelight protests and to political shamelessness.

The record was filed as jazz because the distributors had no other category that fit, he said; in his own description it is closer to contemporary fusion, mixing funk, rock, hip-hop and jazz, and he no longer wanted to be put in a single genre box. W-V=a (June 14, 2021) is an instrumental album of music he wrote for films and videos, with new pieces mixed in. Korean Wikipedia credits him as music director of the films Entry (2013) and Memory (2021), both for Gulliver Pictures, and Melon lists his song "Song for My Girl" on the 2024 soundtrack album Cinematic Novel OST Part.2 (랜선사랑). Deezer also lists him on the 2025 television soundtrack Sold to Love, Part 1. A second Korean book, 지구대표 보컬에겐 'h'가 있다, appeared in 2021.

In the 2023 interview he described himself as a professor in the practical-music department at Yeoju University, teaching vocals, and as a board member (이사) of the Korea Practical Music Education Council (한국실용음악교육협의회); Korean Wikipedia calls him a full-time professor there. He is still performing: a Kyeongin Ilbo listing had his Jamba OJ Band at the Bottom Line jazz club in Incheon's Sinpo district on May 9, 2026.

What is not known: his birthplace, what he studied in France or where, the personnel on his first two albums beyond two guest names on The Story of J (Yonae Seo and Chanhyeun No, as Deezer spells them), and any release details for the Chico Cubo mini-album. He has no Discogs entry, and no English-language press coverage was found.

His voice is described in the release notes for The Story of J as comfortable and warm, and both of his first two albums set out to make jazz feel closer to ordinary Korean listeners: familiar melodies, plain harmony and song forms, a Korean ballad remade as jazz, and a mix of standards with originals that he describes as comforting people tired of life and love. Le Duo is an intimate voice-and-guitar record, and Melon lists bossa nova among its genres. Shame on You is a harder, message-driven record with a rapper, a clean-versus-explicit pair of versions of the title song and a rock and hip-hop edge. On the question of his jazz identity, he told NBN News in 2019 that he had once felt strong pride in being a jazz musician and later decided the genre label mattered less than the music's message.

On whether he is primarily a jazz artist, the evidence favors jazz, with a real pop and soundtrack side. Melon files The Story of J, Competition, Shame on You and W-V=a as jazz (vocal jazz, with acid/fusion/pop added for the first), Deezer files his first four releases as jazz, and Korean Wikipedia places him in its category of Korean jazz singers. He has called himself a jazz vocalist since 2005 and the press calls him the "third-generation" male jazz vocalist in Korea. Against that, he began in pop and rock ballads, describes Shame on You as closer to fusion than jazz, and now spends much of his output on film and television music; Deezer files W-V=a under Asian Music. The tags Vocal Jazz and Jazz Fusion reflect this blend.