Question: Are Johnette Napolitano and Andi Deris both singers?

full_context: Document 1: Concrete Blonde y Los Illegals: An album produced as a joint effort between Johnette Napolitano and James Mankey, previously founding members of alternative rock band Concrete Blonde, and L.A. pachucho punk band Los Illegals. It contains a blend of hard rock and Latin music.
Document 2: Are You Metal?: "Are You Metal?" is a song and a single from German power metal band Helloween's thirteenth studio album 7 Sinners. The single was released physically only in Japan, containing 3 songs. There was also a digital single version available worldwide, which contained only the title song "Are You Metal?", entirely composed by vocalist Andi Deris.
Document 3: Pink Cream 69: Pink Cream 69 is a German Hard rock/heavy metal band founded in 1987 in Karlsruhe, Germany by Andi Deris, Dennis Ward, Kosta Zafiriou and Alfred Koffler. The band gained their first contract by winning music magazine "Metal Hammer" 's newcomer competition in Ludwigsburg one year after forming. In 1994, Andi Deris left the band to join German power metal band Helloween. He was replaced by British singer David Readman.
Document 4: Johnette Napolitano: Johnette Napolitano (born September 22, 1957, Hollywood, Los Angeles, California) is an American singer, songwriter and bassist best known as the lead vocalist/songwriter and bassist for the alternative rock group Concrete Blonde.
Document 5: Michael Kiske: Michael Kiske (born January 24, 1968) is a German singer best known as the lead vocalist for the German power metal band Helloween. After his departure from the band, Kiske recorded four solo albums, participated on various metal and rock related projects, such as Avantasia, Place Vendome and Kiske/Somerville, while he also performed with numerous bands as a guest vocalist. In late 2009, he formed the hard rock / heavy metal band Unisonic and began touring again after 17 years of absence. On November 14, 2016 it was officially announced that Kiske will tour again with Helloween and Kai Hansen in 2017 and 2018.
Document 6: Come In from the Rain (Andi Deris album): Come In from the Rain is the first solo album of Andi Deris, vocalist of the power metal band Helloween. It was released in 1997 and has a different sound from his band's albums, with a different style in each song.
Document 7: Natalie Merchant: Natalie Anne Merchant (born October 26, 1963) is an American singer-songwriter and musician. She joined the American alternative/folk rock band 10,000 Maniacs in 1981 and left it to begin her solo career in 1993. She has since released seven studio albums.
Document 8: Concrete Blonde: Concrete Blonde were an alternative rock band based in the United States. They were active from 1982 to 1995, from 2001 to 2004, and then reunited in 2010 and split up again in 2012. They are best known for their 1990 album "Bloodletting", their top 20 single "Joey", and Johnette Napolitano's distinctive vocal style.
Document 9: Natalie Maines: Natalie Louise Maines (born October 14, 1974) is an American singer-songwriter and activist who achieved success as the lead vocalist for the female alternative country band the Dixie Chicks. Born in Lubbock, Texas, Maines considers herself a rebel who "loved not thinking in the way I knew the majority of people thought."
Document 10: Done by Mirrors: Done by Mirrors is the second solo album of Andi Deris, vocalist of the power metal band Helloween. In Japan, it was released in 1999, but due to record company conflicts, had to be released in 2000 in the rest of the world. The sound is different from Helloween, and from the previous album, "Come in from the Rain", with the dark thematic who would come in 2000 with Helloween's album "The Dark Ride".
Document 11: Joey (Concrete Blonde song): "Joey" is the ninth track from Concrete Blonde's third and most successful album "Bloodletting". The song was released in 1990 and was written and sung by Johnette Napolitano. One interpretation is that the song is about a photographer (Joey Mas) who is in love with alcohol. Napolitano mentioned in her book "Rough Mix" that the song was written about her relationship with Marc Moreland of the band Wall of Voodoo (who would eventually die of kidney failure following a liver transplant).
Document 12: Helloween: Helloween is a German power metal band founded in 1984 in Hamburg, Northern Germany by members of bands Iron Fist and Gentry. Its first line-up consisted of singer and guitarist Kai Hansen, bass guitarist Markus Grosskopf, guitarist Michael Weikath, and drummer Ingo Schwichtenberg. After the release of a self-titled EP and their debut album "Walls of Jericho" in 1985, it expanded into a quintet with the addition of singer Michael Kiske, Hansen choosing to focus on guitar instead. Under this line-up, they released the "Keeper of the Seven Keys" albums (1987 and 1988), which established Helloween as a notable heavy metal band and led to the creation of the power metal subgenre. However, Hansen left the band quickly after the release of "Part II" and was replaced by Roland Grapow. He then created the band Gamma Ray.
Document 13: Andi Deris: Andreas "Andi" Deris (born 18 August 1964) is a German singer and songwriter, best known as the lead vocalist of power metal band Helloween, and co-founder and former lead singer of German melodic metal band Pink Cream 69. He has an active solo career, as well as his own recording studio in Tenerife.
Document 14: Thomas Anders: Thomas Anders (born Bernd Weidung, 1 March 1963) is a German singer, composer, and record producer. Anders was the lead singer of Germany's popular pop-duo Modern Talking in 1983–1987 and in 1998–2003.
Document 15: Alanis Morissette: Alanis Nadine Morissette ( ; ; born June 1, 1974) is a Canadian American alternative rock singer-songwriter, musician, multi-instrumentalist, record producer, and actress. Morissette began her career in Canada in the early 1990s, with two commercially successful dance-pop albums. Afterwards, she moved to Holmby Hills, Los Angeles, and in 1995 released "Jagged Little Pill", a more rock-oriented album which sold more than 33 million units globally and is her most critically acclaimed work. Her following album, "Supposed Former Infatuation Junkie", was released in 1998.
ground_truth: yes