Question: When was the hip hop group formed in which Melvin Glover was a  pioneers of rap as lead rapper?

Context articles: Sindicato Argentino del Hip Hop
Fear of a Black Planet
Treach
Melle Mel
Hip hop
Asociación Hermanos Saíz
B-Real
Grandmaster Flash and the Furious Five
House of Pain
Pee Froiss

Sindicato Argentino del Hip Hop is a hip hop group formed in Argentina.
 They currently consist of three members: Smoler, DJ Fabry and Huexo , and two producers, but they have had different numbers of members over time .
 Their style mainly consists of hip hop and funk.
 The group received a Latin Grammy award in 2001 for best hip hop/rap album.
Fear of a Black Planet is the third studio album by American hip hop group Public Enemy.
 It was released on March 20, 1990, by Def Jam Recordings and Columbia Records.
 For the album, Public Enemy's production team The Bomb Squad sought to expand on the dense, sample-layered sound of the group's 1988 record "It Takes a Nation of Millions to Hold Us Back".
 Having fulfilled their initial creative ambitions with that album, Public Enemy aspired to create what lead rapper Chuck D called "a deep, complex album".
 Their songwriting was partly inspired by the controversy surrounding member Professor Griff and his dismissal from the group in 1989.
Anthony Criss (born December 2, 1970), better known by his stage name Treach, is an American rapper and actor.
 Criss is perhaps best known as the lead rapper of the hip hop group Naughty by Nature.
Melvin Glover (born May 15, 1961), better known as Melle Mel and Grandmaster Melle Mel, is an American hip-hop musician – one of the pioneers of rap as lead rapper and main songwriter for Grandmaster Flash and the Furious Five.
Hip hop or hip-hop is a subculture and art movement developed in South Bronx in New York City during the late 1970s.
 While people unfamiliar with hip hop culture often use the expression "hip hop" to refer exclusively to hip hop music (also called "rap"), Hip hop is characterized by nine distinct elements or expressive realms, of which hip hop music is only four elements (rapping, djaying, beatboxing and breaking).
 Afrika Bambaataa of the hip hop collective Zulu Nation outlined the pillars of hip hop culture, coining the terms: "rapping" (also called MCing or emceeing), a rhythmic vocal rhyming style (orality); DJing (and turntablism), which is making music with record players and DJ mixers (aural/sound and music creation); b-boying/b-girling/breakdancing (movement/dance); and graffiti art, which he called "aerosol writin'", although many say that the graffiti that hip hop adopted had been around years earlier, and had nothing to do with hip hop culture.
 (visual art).
 Other elements of hip hop subculture and arts movements beyond the main four are: hip hop culture and historical knowledge of the movement (intellectual/philosophical); beatboxing, a percussive vocal style; street entrepreneurship; hip hop language; and hip hop fashion and style, among others.
The early/initial visible roots of hip hop in Cuba are believed to have emerged through break dance competitions or battles that were seen on the streets of Cuba.
 The continuous repetition of break dance battles were one of the strong channels or pioneers of the hip hop culture in Cuba.
 Some sources state that hip hop in Cuba strongly emerged in the early nineties as a way out due to the "termination" of the numerous subsidies that were received by the country through the Soviet.
 All the above-mentioned pertaining to Cuban hip hop is vital however, none of it would have been successful without the presence of one of the two Cuban Institutions namely, Asociacion Hermanos Saiz and Agencia Cubana de Rap (Cuban Rap Agency).
 Asociacion Hermanos Saiz and the latter are the two initial Institutions that were funded by the Cuban Government with the major motive of promoting Rap/hip hop in Cuba more so, hip hop groups in Cuba.
Louis Freese (born June 2, 1970), better known by his stage name B-Real, is an American rapper and actor.
 He is best known for being the lead rapper in the hip hop group Cypress Hill and one of two rappers in the rap rock supergroup Prophets of Rage.
Grandmaster Flash and the Furious Five were an American hip hop group formed in the South Bronx of New York City in 1976.
 Composed of one DJ (Grandmaster Flash) and five rappers (Melle Mel, The Kidd Creole, Keith Cowboy, Mr. Ness/Scorpio, and Rahiem), the group's use of turntablism, break-beat deejaying, and conscious lyricism were significant in the early development of hip hop music.
House of Pain is an American hip hop group who released three albums in the 1990s before lead rapper Everlast left to pursue his solo career.
 The group's name is a reference to the H.G. Wells novel "The Island of Dr. Moreau", a reference carried further by the naming of their 2011 tour "He Who Breaks the Law".
 The group is best known for its 1992 hit single "Jump Around", which reached No. 3 in their native United States, No. 6 in Ireland and No. 8 in the United Kingdom.
 The group broke up in 1996 but reformed in 2010, after the trio had been members of supergroup La Coka Nostra for several years.
Pee Froiss is a hip hop group formed in Dakar, Senegal in 1993.
 It was originally produced by another hip hop group from that city, Positive Black Soul, and since recorded with the duo.
 The band's music is rapped in Wolof, French, and English and features traditional Senegalese instruments such as the kora as part of its instrumentation.
 Pee Froiss was one of the first rap groups to include a female performer in their lineup, Sista Joyce.
 The group's members create all of their own music videos with very sparse resources, the first of which was released in 1996 with their first album.