Young-Soo Yoo (유영수) is a Seoul drummer known only through his credits. No source found gives his birth date or birthplace, a biography, an interview of his own or a photograph, and he has no record under his own name. What can be shown is a working life on records and in jazz clubs from 1971 to at least 2012, all of it in Korea. Korean newspapers print his name as 유영수 and romanize it variously as Yu Yeong-su, Yoo Young-soo or Young-Soo Yoo; Discogs files the credits discussed here under "Young-Soo Yoo" (artist 3194839), with 유영수 as a name variation. This profile uses that billing, which is how Discogs prints his name in the credits of the 1971, 1974, 1975, 1976, 1979 and 1987 records below. Whether he is still alive or playing is not known.

His earliest dated credit is the debut album of the folk singer Kim Min-ki (김민기), released on October 21, 1971 (Taedo, EU 716). On four tracks, "아하 누가 그렇게...", "바람과 나", "길" and "종이연", Discogs credits him on drums with the saxophonist and flutist Jung Sung-jo (정성조), who arranged the album, the bassist Jo Won-ik (조원익) and a pianist credited as Son Soo Gil. In a 2002 interview with the music writers Shin Hyun-joon and Choi Ji-seon, Jung was asked about the Kim Min-ki and Yang Hee-eun records and answered that the drummer then was Yu; the interview does not name tracks, and Discogs credits him on no Yang Hee-eun record.

The same interview and a band photograph place him in the Messengers, the electric group Jung formed around 1972 or 1973. The photograph's caption lists the trumpeter Choi Sun-bae (최선배), Yu on drums, the bassist Jo Gyeong-su (조경수) and Jung. On record, Discogs credits him on both Messengers LPs, It Rained Yesterday (Shin Segye Record, S가 8014, 1975) and Yeong-ja's Heyday (Shin Segye Record, S가 8027, February 1976), with Choi on trumpet; both are film soundtracks, and Discogs files them under funk and soul, pop, and stage and screen rather than jazz. Later pressings dated 1977 and 1978 carry his credit as well. A year before the first of them, in April 1974, he is the drummer on the soundtrack LP for the film Home of the Stars (별들의 고향; Sung Eum Limited, SEL-20-0029) by the singer Lee Jang-hee (이장희) and the guitarist Kang Geun-sik (강근식), with Jo Won-ik on bass and Choi on trumpet. Discogs lists jazz among that LP's genres, beside rock, funk and soul, and pop. A Kyunghyang Shinmun and MBC report of January 17, 2012 calls Kang, Jo and Yu the original members of Lee Jang-hee's band 동방의 빛, reunited after about 40 years for Lee's first concert in 23 years, recorded at the MBC Dream Center on January 8, 2012. It is the latest dated appearance found.

The Janus mentions are all in the press. The club Janus opened in 1978 in Sinchon, Seoul, founded by the singer Park Seong-yeon (박성연). The Yeongnam Ilbo wrote in 2017 that Yu and Choi Sun-bae joined its players after the first members. The Hankook Ilbo's 2010 profile of Lee Pan-geun (이판근) names him among those who played Lee's monthly concerts there, beside Kang Dae-gwan (강대관), Choi Se-jin (최세진), the guitarist Cho Jeong-su (조정수), Kim Soo-yeol (김수열), Son Soo-gil (손수길) and Park. In a January 2011 interview the pianist Shin Kwan-woong (신관웅) recalled first taking the stage at Janus with Park, who sang, and Yu, who played drums. None of these accounts gives the years of his time at the club.

His one jazz album credit is Land of Morning Calm (Early Spring in Seoul) (Oasis Records, OL-2761, March 1987) by the Shin Kwan Woong Jazz Quartet: Shin on piano and as arranger and conductor, Ham Ki-ho (함기호) on bass, Kim Soo-yeol on tenor saxophone, Yu on drums, and Kim Jun (김준) as producer. Its eight tracks pair "Take the 'A' Train", "Satin Doll" and "All Blues" with the Korean pieces "Blues Arirang", "한오백년" and "돌아와요 부산항에". Elsewhere his credits are on disco and folk-era pop: in October 1979 Discogs lists him, with Ryu Bok-sung (류복성), Kim Kwang-seok, Lee Chul-hyuk and Lee Yu-sin, as credited for instruments on the Daedo Records LP Non-Stop Disco Party (DSAP-79009), a set of fifteen disco covers.

Discogs holds four further entries with near-identical names, among them a second 유영수 (see the discography); a 1984 Kim Jun album, a 1993 Lee Jung-sik album and a 2011 quintet album are among their credits. No source found shows that any of them is the same man, so none is counted here.

Nothing found describes how he played, and he is not quoted anywhere. All that can be said from the records is the range of work: a folk singer's debut with a jazz saxophonist arranging, brass-led electric soundtrack records with the Messengers, a film soundtrack LP that Discogs files across jazz, rock, funk and pop, a disco covers album and one straight jazz quartet LP of standards and Korean melodies. Discogs and the press agree on the jazz side only for the 1987 album and the Janus club; the rest is session and band work outside jazz, so the Mainstream Jazz tag rests on the 1987 record and on the club.