Question: Mark Stuart and Vincent Walker both are known as what in their bands?
Context: Brian Robertson (born October 19, 1979) is the trombone player for the Orange County-based third-wave ska band Suburban Legends and, along with Vincent Walker, is one of the two members to have played with the band since its origin as Bomb Squad.  He met other ex-Suburban Legends / Bomb Squad members, trumpet player Aaron Bertram and best friend and trombone player Ryan Dallas Cook through the Huntington Beach High School Marching Band.  In 2007, Robertson started to be known by the nickname 'Robot', most likely a reference to the dance moves he does onstage with the band, the first three letters of his last name, and/or to avoid confusion with the band's other Brian, Brian Klemm. Day Job is Suburban Legends' fifth album, released on April 3, 2012.  Aaron Bertram, Brian Robertson, Derek Rock, and Vincent Walker appeared on local online radio program "TNN Radio" to announce the album on February 18, 2012. Mark Allen Stuart (born April 14, 1968) is a Christian rock musician, singer and songwriter best known as the lead vocalist for the Christian rock band Audio Adrenaline during their original run from 1987 to 2006. Vincent Walker "Vince" Foster Jr. (January 15, 1945 – July 20, 1993) was a Deputy White House Counsel during the first half-year of President Bill Clinton's administration.  Prior to that, he was a partner at Rose Law Firm in Little Rock, Arkansas, where he was a colleague and friend of Hillary Rodham Clinton and where, as "The Washington Post" later wrote, he rose to "the pinnacle of the Arkansas legal establishment."  At the White House he was unhappy with work in politics and spiraled into depression.  His death by gunshot was attributed by five official or governmental investigations to suicide but several conspiracy theories emerged. Charles Vincent Walker FRS (20 March 1812 – 24 December 1882) was an English electrical engineer and publisher, a major influence on the development of railway telecommunications, he was also the first person to send a submarine telegraph signal. The Know Hope Collective was an American worship and testimonial project formed by Mark Stuart and Will McGinniss, former members of the Grammy Award-winning Christian rock band Audio Adrenaline.  Emerging out of the fallout from the disbandment of Audio Adrenaline and Mark Stuart’s personal problems, the project has been described by Stuart and McGinniss, as "an ever-changing group of musicians from a variety of backgrounds who come together to create worship music while sharing their unique experiences and testimonies," and "a ground-breaking initiative that combines worship music with stories of hope and inspiration."  Stuart further elaborated it as being "driven from an emerging style of worship and a place of vulnerability.  We go on a journey together through the good, bad and ugly to the redemptive side."  The project’s self-titled debut album was released March 1, 2011. Vincent Francis Walker (born March 2, 1980), better known as Vince Walker, is an American multi-instrumentalist, best known as the lead singer of third-wave ska band Suburban Legends.  He was formerly the lead trumpet player, and left sometime after the release of "Rump Shaker", but returned to the band in September 2005 for the band's appearance on the Jerry Lewis MDA Telethon, which happened to be lead singer Tim Maurer's last performance.  He replaced Maurer as the singer in an odd switching of roles, and continues with the band as frontman. Billy Bang (September 20, 1947 – April 11, 2011), born William Vincent Walker, was an American free jazz violinist and composer. Timothy Robert "Tim" Maurer (born October 10, 1980) is an American singer, best known as the former lead singer of third-wave ska band Suburban Legends.  He has left the band on two separate occasions.  The first was in 2000 after the recording of Origin Edition.  He rejoined the band in early 2002 after his replacement singer Chris Batstone left the band.  He officially left the band again in September 2005 after the band's third consecutive appearance on the Jerry Lewis MDA Telethon, performing a new song entitled "Moving Closer."  The band's former trumpet player, Vincent Walker, rejoined the band for the performance, then took over as lead singer afterward.  Maurer returned for a final performance with the band on November 29, 2005 at Huntington Beach High School for a benefit show for the Ryan Dallas Cook Memorial Fund, which was set up following the death of Suburban Legends' trombonist Dallas Cook. Michael B. Stuart (born August 31, 1980 in Rochester, Minnesota) is a professional ice hockey player who currently plays for Lørenskog of the Norwegian Eliteserien.  Mike is the brother of Mark Stuart and Colin Stuart.
Answer: singer