Question: Which producer of Zeitgeist was also the lead singer?
Context: Alexander Martin Barr (born January 21, 1968) has been the lead singer of the Dropkick Murphys since 1998.  He was also a founder and lead singer for The Bruisers, which he helped form in 1988 in Portsmouth, New Hampshire.  His first band circa 1984, was called D.V.A. (Direct Vole Assault).  He also went on to front 5 Balls of Power, with future members of Scissorfight, The Radicts, L.E.S. Stitches, and US Bombs, before he formed The Bruisers.  His band the Bruisers had played many shows with Boston's Dropkick Murphys, and when Dropkick lead singer Mike McColgan quit the band in 1998 the Murphys asked Barr to be the new lead singer.  The first album the Dropkick Murphys released with Barr as singer was 1999's "The Gang's All Here". Pete Stewart is a singer, guitarist, songwriter and producer from Seattle, Washington.  He is the lead singer and guitarist of Grammatrain, was the lead singer for The Accident Experiment, and is the former guitarist of Tait. Zeitgeist is the seventh album by American alternative rock band The Smashing Pumpkins, released on July 10, 2007 in the United States and Canada.  It was the first album The Smashing Pumpkins released after their 2000 disbandment and 2005 reunion.  The album was produced by Roy Thomas Baker, Billy Corgan, Jimmy Chamberlin, and Terry Date.  The album would be Chamberlin's last with the band before his departure in 2009.  The album debuted strongly, but sales soon decreased, and critical reception was mixed.  It was certified Gold in the United States on February 1, 2008. Shirley Alston Reeves (born Shirley Owens June 10, 1941, Henderson, North Carolina) is an American soul singer who was the main lead singer of the hit singing group the Shirelles.  In addition to Owens, the Shirelles consisted of classmates of hers from Passaic High School, New Jersey:Doris Kenner Jackson, Addie "Micki" Harris and Beverly Lee.  Through marriages, she became Shirley Alston and later, Shirley Alston Reeves.  Her strong, distinctive voice meant that she was the natural choice for their main lead singer, though Jackson was also featured as lead on several songs as well.  Her nephew, Gerald Alston is the lead singer of The Manhattans. Diana Ernestine Earle Ross (born March 26, 1944) is an American singer, songwriter, actress, and record producer.  Born and raised in Detroit, Michigan, Ross rose to fame as the lead singer of the vocal group The Supremes, which, during the 1960s, became Motown's most successful act, and is to this day the United States' most successful vocal group, as well as one of the world's best-selling girl groups of all time.  Ross' success as lead singer of The Supremes made it possible for future African-American R&B and soul acts to find mainstream success.  The group released a record-setting twelve number-one hit singles on the US "Billboard" Hot 100, including "Where Did Our Love Go", "Baby Love", "Come See About Me", "Stop!  In the Name of Love", "You Can't Hurry Love", "You Keep Me Hangin' On", "Love Child", and "Someday We'll Be Together". William Patrick "Billy" Corgan Jr. (born March 17, 1967) is an American musician, songwriter, producer, poet, and entrepreneur.  He is best known as the lead singer, primary songwriter, guitarist, and sole permanent member of The Smashing Pumpkins.  Formed by Corgan and guitarist James Iha in Chicago, Illinois, in 1988, the band quickly gained steam with the addition of bassist D'arcy Wretzky and drummer Jimmy Chamberlin.  Strong album sales and large-scale tours propelled the band's increasing fame in the 1990s until their break-up in 2000.  Corgan started a new band called Zwan, and after their quick demise, he released a solo album ("TheFutureEmbrace") and a collection of poetry ("Blinking with Fists") before setting his sights on reforming Smashing Pumpkins. Michael Allan "Mike" Patton (born January 27, 1968) is an American musician, singer, songwriter, actor, record producer, multi-instrumentalist and film composer, best known as the lead singer of the alternative metal band Faith No More.  Patton was also the founder and lead singer of Mr. Bungle, and has played with Tomahawk, Fantômas, Lovage, The Dillinger Escape Plan, and Peeping Tom. Adolf "Dado" Topić (born 4 September 1949, Siverić) is a rock musician from Croatia and the former Yugoslavia.  He was the lead singer and founder of Time, a 1970s progressive rock band.  From 1970 to late 1971, he was also the lead singer of the popular prog-rock band Korni Grupa (also known as The Kornelyans).  He is a rock musician from Croatia and the former Yugoslavia.  He was the lead singer and founder of Time, a 1970s progressive rock band.  From 1970 to late 1971, he was also the lead singer of the popular prog-rock band Korni Grupa (also known as The Kornelyans).  He is a male vocalist who sang the entry from Croatia in the Eurovision Song Contest 2007, together with the band Dragonfly. The Passions are an American doo-wop group from Bensonhurst, Brooklyn.  The quintet recorded a few demos in 1958, at which time Tony, Albee and Vinny began looking for replacements who were more career-minded.  Another group in Bensonhurst had what they needed; when the three Sinceres heard Runarounds lead singer Jimmy Gallagher, they knew he was the one for them (Jimmy’s previous group, the Palladiyms, included Joe DiBenedetto, who later formed "The Four-evers".) The Sinceres weren’t sure how to approach Jimmy, so they followed him home one night and knocked on his door.  After convincing his mother that they only wanted to sing with her son, not mug him, the foursome went to a nearby park and ended up harmonizing for hours.  They were now a quartet, with Jimmy on lead, Tony on first tenor, Albee on second tenor, and Vinnie on baritone.n 1959, while the Mystics were recording "Hushabye" at their first session, their friend Tony Armato was there cheering them on promoting his own group to their manager, Jim Gribble.  Gribble soon signed the Sinceres and renamed them the Passions.  He gave them a demo by a duo of studio singers who called themselves the Cousins.  The song was "Just to Be with You" written by Mary Kalfin.  The Cousins were Paul Simon and Carole King.  By the time the group recorded "Gloria" Vinny had left and been replaced by Gallagher’s friend Lou Rotondo.  Also in 1960 Lou Rotondo and Albie Galione, along with Albie Contrera of the Mystics, sang behind Clay Cole on "Here, There, Everywhere" (Roulette), single that became popular in the New York area.  Audicon Records lost the group’s next release, the harmony rocker "Made for Lovers."  The group recorded a few more sides for Audicon which were leased to Jubilee and Octavia.  Released in August 1959 on Sol Winkler’s Audicon label, the Passions’ impeccable harmonies and Gallagher’s impassioned lead put "Just to Be with You" on radios across America.  It was a top 20 hit in many eastern cities and it charted nationally, rising to number 69.  The follow-up out of Audicon’s 1674 Broadway digs was twice as good.  Both sides—the harmony filled "I Only Want You" and the beautiful Billy Dawn Smith ballad "This Is My Love" –vied for radio play and sales throughout the states.  They were managed by Jim Gribble who managed several doo-wop groups including the Mystics and The Jarmels, and worked with producer songwriter Stan Vincent.  In the late 1990s, they reunited with the Mystics and the Classics for the Brooklyn Reunion Show.  Lead singer Jimmy Gallagher left the Passions in 1960 to join the Navy, but later sang with The Legends of Doo Wop in 1998. Sennie "Skip" Martin III (born June 25, 1957, in San Francisco, California, U.S.) is an American musician, now based in Las Vegas.  He is a lead vocalist, trumpet player, songwriter and producer who was formerly lead vocalist for Kool & The Gang (1987–2007) and the Dazz Band.  Before those groups he was lead singer for the East Wind Band and then he was lead singer for the Mighty Generation Band.  With the Dazz Band he won a Grammy Award for the song “Let It Whip”.
Answer: Billy Corgan