Question: Graham Bonnet and John Corabi, have which mutual occupation?

Context paragraphs:
Brides of Destruction: Brides of Destruction was a short-lived American hard rock supergroup from Los Angeles, California, formed in 2002.  The band's last lineup consisted of singer London LeGrand (vocals), Tracii Guns (lead guitar) and Scot Coogan (drums, percussion).  Previous members of the band were Nikki Sixx (bass), Kris Kohls (drums), Adam Hamilton (keyboard), John Corabi (rhythm guitar), Scott Sorry (bass) and Ginger (rhythm guitar).

Union (band): Union is an American rock group formed in 1997 featuring lead vocalist and guitarist John Corabi (ex-The Scream and Mötley Crüe), guitarist Bruce Kulick (ex-Kiss), bassist James Hunting (David Lee Roth and Eddie Money), and drummer Brent Fitz (Slash).

Hooligan's Holiday: "Hooligan's Holiday" is a song by American heavy metal band, Mötley Crüe, released on their 1994 eponymous album.  The lyrics to the song were written by vocalist/rhythm guitarist John Corabi and bassist Nikki Sixx, while the music was written by Corabi, Sixx, drummer Tommy Lee and guitarist Mick Mars.

The Day I Went Mad: The Day I Went Mad is the sixth solo album by English rock singer Graham Bonnet, originally released in 1999.  Much like his previous solo efforts, Bonnet enlisted a host of guest musicians for the recording, including former Guns N' Roses guitarist Slash, Def Leppard guitarist Vivian Campbell and Vanilla Fudge bassist Tim Bogert.  The album cover was illustrated by guitarist Mario Parga, who plays on several tracks.

John Corabi: John Corabi (born April 26, 1959) is a hard rock singer and guitarist who has worked with such bands as Angora, The Scream, Mötley Crüe, Union and ESP (both with former Kiss lead guitarist Bruce Kulick), Ratt (as a guitarist), Twenty 4 Seven (with his then Ratt bandmate Bobby Blotzer), Zen Lunatic, Brides of Destruction, and Angel City Outlaws (with his then Ratt bandmates Robbie Crane and Bobby Blotzer, and former Ratt guitarist Keri Kelli, who he replaced in Ratt).  He is the current lead singer for The Dead Daisies.

Graham Bonnet: Graham Bonnet (born 23 December 1947) is an English rock singer and songwriter.  He has recorded and performed as a solo artist and as a member of several hard rock and heavy metal bands including Rainbow, the Michael Schenker Group, Alcatrazz, and Impellitteri.  Bonnet is known for his James Dean-inspired style and extremely powerful singing voice and wide vocal range.  His singing has been noted as 'very loud' by both his contemporaries and himself, and he claims to be a self-taught singer with 'no discipline for lessons'.

Misunderstood (Mötley Crüe song): "Misunderstood" is a power ballad by the American heavy metal band Mötley Crüe, released on their 1994 eponymous album.  The lyrics were written by vocalist/guitarist John Corabi and bassist Nikki Sixx, while the music was written by Corabi, Sixx, drummer Tommy Lee and guitarist Mick Mars.  The song charted at number 24 on the Mainstream rock charts.

Mötley Crüe (album): Mötley Crüe is the eponymous sixth studio album by American heavy metal band Mötley Crüe.  It was released on March 15, 1994, and is the only album that does not feature lead singer Vince Neil, who had departed from the band in 1992.  Neil was replaced by former The Scream vocalist John Corabi on the album.

Eric Singer Project: Eric Singer Project is an American rock band.  ESP was founded in the 1990s by Eric Singer, drummer for such acts as Lita Ford, Black Sabbath, Badlands, Alice Cooper, and Kiss, along with Bruce Kulick (Kiss, Grand Funk Railroad) on guitar, John Corabi (The Scream, Mötley Crüe, Ratt) on guitar and bass, and Karl Cochran on guitar and bass.  Vocals duties were shared by Eric, John, and Karl.

Underground (Graham Bonnet album): Underground is the fifth solo album by English rock singer Graham Bonnet, originally released in 1997.  "Underground" reunites Bonnet with guitarist Danny Johnson, who previously performed with Bonnet in Alcatrazz.  "Lost in Hollywood" is a re-recording of a song Bonnet recorded during his tenure with Rainbow.

Supporting paragraphs: Graham Bonnet John Corabi
Answer: rock singer