Question: What occupation is shared by Luca Prodan and Glenn Gregory?

full_context: Document 1: Steve Strange: Steven John Harrington (28 May 1959 – 12 February 2015), better known by his stage name Steve Strange, was a Welsh pop singer. From the late 1970s he was a nightclub host and promoter. He became famous as the leader of the new wave synthpop group Visage, best known for their single "Fade to Grey", and was one of the most influential figures behind the New Romantic movement of the early 1980s.
Document 2: Luca Prodan: Luca Prodan (17 May 1953 – 22 December 1987) was an Italian–Scotish musician and singer. He was the leader and singer of Sumo, one of the most influential rock bands of Argentina, and is widely considered as one of the most important artists of the last quarter of the twentieth century in his country.
Document 3: Dave Gahan: David "Dave" Gahan ( ; born David Callcott; 9 May 1962) is an English singer-songwriter, best known as the baritone lead singer of the electronic band Depeche Mode since their debut in 1980. He is also an accomplished solo artist, releasing albums in 2003 ("Paper Monsters") and 2007 ("Hourglass").
Document 4: Gary Numan: Gary Anthony James Webb (born 8 March 1958), known professionally as Gary Numan, is an English singer, songwriter, composer, musician and record producer. Born in Hammersmith, West London, he first entered the music industry as lead singer of the new wave band Tubeway Army. After releasing two studio albums with the band, Numan released his debut solo album "The Pleasure Principle" in 1979.
Document 5: Sumo (band): Sumo was a 1980s Argentine alternative rock band, merging "post-punk" with "reggae". Headed by Italian-born Luca Prodan, it remained underground for most of its short activity, but was extremely influential in shaping contemporary Argentine rock. Sumo introduced British post-punk to the Argentine scene, with many lyrics in English. And provided a visceral counterpoint to the progressive and nueva canción influences then dominant in "Rock en Español".
Document 6: Boy George: Boy George (born George Alan O'Dowd; 14 June 1961) is an English singer, songwriter, DJ, fashion designer and photographer. He is the lead singer of the Grammy and Brit Award-winning pop band Culture Club. At the height of the band's fame, during the 1980s, they recorded global hit songs such as "Do You Really Want to Hurt Me", "Time (Clock of the Heart)" and "Karma Chameleon" and George is known for his soulful voice and androgynous appearance. He was part of the English New Romantic movement which emerged in the late 1970s to the early 1980s.
Document 7: Lucio Battisti: Lucio Battisti (5 March 1943 – 9 September 1998) was an Italian singer and composer. He is considered to be one of the best-known and most influential musicians and authors in Italian pop/rock music history.
Document 8: Glenn Gregory: Glenn Peter Gregory (born 16 May 1958) is an English singer, songwriter, and multi-instrumentalist whose music career spans more than 30 years. He came to prominence in the early 1980s as co-founder and lead singer of the new wave and synthpop band Heaven 17, which released six singles that entered the Top 40 charts in the United Kingdom during the 1980s, and 1990s, including "Temptation", "Come Live with Me", "Crushed by the Wheels of Industry", "Sunset Now", "This Is Mine", and "(We Don't Need This) Fascist Groove Thang" .
Document 9: Divididos: Divididos ("Divided") is an Argentine rock band. The band was formed in 1988 after the death of Luca Prodan and the consequent dissolution of the band Sumo. Ricardo Mollo (vocals, guitar) and Diego Arnedo (bass guitar) joined drummer Gustavo Collado to form a band named "La División" (The Division), which would be later called "Divididos".
Document 10: Andrea Prodan: Andrea Prodan (born 16 November 1961) Scottish-Italian film actor, composer and musician is the younger brother of Argentine rock star Luca Prodan. The Prodan family, after suffering internment in a Japanese concentration camp during WW II, was expelled from China due to Mao. Andrea's Italian father was an author and talented sportsman, and had run a prosperous business, with expertise in ancient Chinese pottery. His mother is Scottish.
Document 11: Gary Glitter: Paul Francis Gadd (born 8 May 1944), known by the stage name Gary Glitter, is an English former glam rock singer, who achieved popular success in the 1970s and 80s. He was known for his extreme glam image of glitter suits, make-up and platform boots, and his energetic live performances. He sold over 20 million records, spent 168 weeks on the UK Singles Chart and had 21 hit singles placing him in the Top 100 UK most successful chart acts. From 1997, he returned to public notice for committing sex offences, being imprisoned for downloading child pornography in 1999, and child sexual abuse and attempted rape in 2006 and 2015.
Document 12: Heaven 17: Heaven 17 are an English new wave and synth-pop band that formed in Sheffield in 1980. The band were a trio for most of their career, composed of Martyn Ware (keyboards), Ian Craig Marsh (keyboards) (both previously of the Human League) and Glenn Gregory (vocals). Although most of the band's music was recorded in the 1980s, they have occasionally reformed to record and perform, playing their first ever live concerts in 1997. Marsh left the band in 2007 and Ware and Gregory continued to perform as Heaven 17.
Document 13: Luca Turilli: Luca Turilli (born 5 March 1972) is an Italian musician (primarily a guitarist) and songwriter. He is one of the founders of the symphonic power metal band Rhapsody of Fire. He also worked on a trilogy of solo albums as Luca Turilli, and released one album under the name of Luca Turilli's Dreamquest, a project he worked on alongside Dominique Leurquin. In 2008, Luca began an online guitar course titled "Luca Turilli's Neoclassical Revelation". The course takes its name from his neoclassical playing style.
Document 14: Glenn Hughes: Glenn Hughes (born 21 August 1951) is an English rock bassist and vocalist, best known for playing bass and performing vocals for funk rock pioneers Trapeze, the Mk. III and IV line-ups of Deep Purple, as well as briefly fronting Black Sabbath in the mid-1980s.
Document 15: Las Pelotas: Las Pelotas (in English: "The Balls"); is an Argentine band rock and reggae, from Córdoba. This band was formed after the separation of Sumo, due to the death of their singer, Luca Prodan in 1987. The group currently consists of vocalist and guitarist, Germán Daffunchio, Gabriela Martínez on bass, Tomás Sussman on guitar, Sebastián Schachtel on Keyboards and Gustavo Jove on drums. Their original vocalist, Alejandro Sokol, was part of the band from 1988 to 2008; year that begins his solo career, cut short by his sudden death in 2009.
ground_truth: singer