Question: Adam Levine and Gwen Stefani, are American with which mutual occupations?

Context articles: The Voice (U.S. season 9)
The Voice (U.S. season 10)
The Voice (U.S. season 8)
Adam Levine
Sunday Morning (No Doubt song)
Gwen Stefani
The Voice (U.S. season 12)
Viktor Király
What You Waiting For?
The Voice (U.S. season 13)

The ninth season of the American reality talent show "The Voice" premiered on September 21, 2015 on NBC.
 Adam Levine, Blake Shelton, Pharrell Williams, and Gwen Stefani returned as coaches for the season.
The tenth season of the American reality talent show "The Voice" premiered on February 29, 2016 on NBC.
 Carson Daly returned as the show's host.
 Adam Levine, Blake Shelton, and Pharrell Williams all returned as coaches, while Christina Aguilera returned after a one-season hiatus.
 Gwen Stefani did not return as a coach for this season, but was the advisor for Team Blake in the Battle Rounds.
The eighth season of the American reality talent show "The Voice" premiered on February 23, 2015 on NBC.
 Carson Daly returned as host.
 Adam Levine, Blake Shelton, and Pharrell Williams returned as coaches.
 Gwen Stefani did not return for season eight, making room for the return of Christina Aguilera after a two-season absence.
 Sawyer Fredericks, of Team Pharrell, won the competition.
Adam Noah Levine (born March 18, 1979) is an American singer, songwriter, multi-instrumentalist, actor, and record producer.
 He is the lead singer for the pop rock band Maroon 5.
"Sunday Morning" is a song recorded by American rock band No Doubt.
 It was released as the sixth single from their third studio album "Tragic Kingdom" (1995).
 The single was made available as a CD single, cassette single, and VHS single on May 27, 1997 through Interscope.
 Lyrically, the song is about Gwen Stefani's relationship with Tony Kanal, and their breakup that followed.
 The track was written by band members Kanal, Gwen Stefani, and Eric Stefani, while production was handled by Matthew Wilder.
Gwen Renée Stefani ( ; born October 3, 1969) is an American singer, songwriter, fashion designer, actress, and television personality.
 She is a co-founder and the lead vocalist of the band No Doubt that experienced major success after their breakthrough studio album "Tragic Kingdom" (1995) along with various successful singles, including "Just a Girl", "Don't Speak", "Hey Baby", and "It's My Life".
 During the band's hiatus, Stefani embarked on a solo pop career in 2004 by releasing her debut studio album "Love.
 Angel.
 Music.
 Baby.
" Inspired by pop music from the 1980s, the album was met with both critical and commercial success.
 It spawned three commercially successful singles: "What You Waiting For?
", "Rich Girl", and "Hollaback Girl", the latter reached number one on the "Billboard" Hot 100 while also becoming the first US download to sell one million copies.
 In 2006 Stefani released her second studio album "The Sweet Escape".
 The album produced two successful singles: "Wind It Up" and the album's title track "The Sweet Escape".
 Her third solo album "This Is What the Truth Feels Like" was released in March 2016 and became her first solo number-one album on the "Billboard" 200.
The twelfth season of the American reality talent show "The Voice" premiered on February 27, 2017 on NBC with Gwen Stefani and Alicia Keys returning as coaches alongside Adam Levine and Blake Shelton.
Viktor Király (born 29 March 1984) is a Hungarian-American singer.
 In 2006, he was part of the Hungarian band Twinz with his twin brother Benjamin.
 In 2008, he became the fourth winner of the Hungarian music competition "Megasztár".
 He is the younger brother of the Hungarian pop singer Linda Király.
 In 2012 and 2014, he took part in "A Dal", a selection process in an unsuccessful bid to represent Hungary in the Eurovision Song Contest.
 In 2015, he took part in season 9 of the American series "The Voice", initially as part of Adam Levine's team, and later Gwen Stefani's, but was eliminated on 11 November during the Live Playoffs round, in which the Top 24 competed for the public's vote and coaches' choices.
"What You Waiting For?"
 is a song by American singer Gwen Stefani from her debut solo studio album, "Love.
 Angel.
 Music.
 Baby.
" (2004).
 Written by Stefani and Linda Perry, the song is the album's opening track and was released as Stefani's debut solo single.
 "What You Waiting For?"
 details Stefani's lack of inspiration, fear of producing the album, as well as her reaction to pressures exerted by her record label.
 It is primarily an electropop song and introduces Stefani's four back-up dancers, the Harajuku Girls, who had a major input into the album's production.
The thirteenth season of the American reality talent show "The Voice" premiered on September 25, 2017, on NBC.
 Adam Levine and Blake Shelton returned as coaches.
 Miley Cyrus and Jennifer Hudson replaced Gwen Stefani and Alicia Keys as coaches.