Question: Which singer is also a musician, Gwen Stefani or Charlie Simpson?

 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. Gwen Renée Stefani ( ; born October 3, 1969) is an American singer, songwriter, fashion designer, actress, and television personality.  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. <SEP>  He is the youngest member of multi-BRIT Award-winning band Busted, and is the lead vocalist, guitarist in post-hardcore band Fightstar.  AllMusic has noted that Simpson is "perhaps the only pop star to make the convincing transition from fresh-faced boy bander to authentic hard rock frontman". Charles Robert "Charlie" Simpson (born 7 June 1985) is an English singer, songwriter and musician.  Simpson is a multi-instrumentalist, playing guitar, keyboard, piano and drums. <SEP> American singer and songwriter Gwen Stefani has recorded material for three studio albums and one extended play (EP), and has been featured on songs on other artists' respective albums.  After releasing five studio albums with ska punk group No Doubt, in 2004 Stefani began work as a solo artist, developing her pop debut "Love.  Angel.  Music.  Baby. " in the same year.  It produced several top ten singles worldwide, including "What You Waiting For? ", "Rich Girl", and "Hollaback Girl", the latter of which was the first single to sell over a million digital copies in the United States.  The record contained work from a variety of producers and songwriters, including Linda Perry, Nellee Hooper, André 3000, and No Doubt bandmate Tony Kanal. " Cool", "Luxurious", and "Crash" were also released as the singles.  In 2005, Stefani released an extended play "Love.  Angel.  Music.  Baby.  (The Remixes)" and included the Richard X remix of "Cool", which topped the United States Dance Club Songs in November 2005.  Hip hop musician André 3000 made two appearances on the album, including on "Long Way to Go", and his alter ego "Johnny Vulture" on "Bubble Pop Electric". <SEP> "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.