Question: Which singer was the leader of an alternative rock band,  Bob Mould or Hayley Williams?

Context paragraphs:
Poison Years: Poison Years is a compilation album by Bob Mould, who had been the guitarist and co-vocalist of the influential American rock band Hüsker Dü.  It is essentially a condensed version of Mould's first two solo albums on Virgin Records, "Workbook" (1989) and "Black Sheets of Rain" (1990), and was released in mid-1994 after Mould had achieved considerable success with his new band Sugar.  It contains 6 (out of 11) studio tracks from "Black Sheets" and 5 (out of 11) tracks from "Workbook", of which 3 are previously unreleased live versions.  In addition, the album contains a studio outtake from the "Workbook" period, "All Those People Know", a live version of another non-album track, "If You're True", and a live cover version of "Shoot Out The Lights" from the eponymous 1982 album by Richard and Linda Thompson.

Sugar (American band): Sugar was an American alternative rock band of the early 1990s.  Formed in 1992, they were led by the singer and guitarist Bob Mould (ex-Hüsker Dü), alongside bassist David Barbe (ex-Mercyland) and drummer Malcolm Travis (ex-Human Sexual Response).

Hayley Williams: Hayley Nichole Williams (born December 27, 1988) is an American singer, songwriter and musician.  She serves as the lead vocalist, primary songwriter and occasional keyboardist of the rock band Paramore.  The band was formed in 2004 by Josh Farro, Zac Farro, Jeremy Davis and Williams.  The band consists of Hayley Williams, Zac Farro and Taylor York.  The band has five studio albums: "All We Know Is Falling" (2005), "Riot! " (2007), "Brand New Eyes" (2009), "Paramore" (2013) and "After Laughter" (2017).

Copper Blue: Copper Blue is the debut studio album by American alternative rock band Sugar.  It was voted 1992 Album of the Year by the NME.  All of the songs were written by guitarist/vocalist Bob Mould, who also co-produced with Lou Giordano.  The song "The Slim" is about losing someone to AIDS.  Musically, the band continues the thick punk guitar of Mould's previous band, Hüsker Dü, while slowing the tempo and emphasizing melody even more.

Workbook (album): Workbook is the 1989 debut solo album by American guitarist and singer Bob Mould, following the breakup of the influential rock band Hüsker Dü.  The album has a strong folk influence and lighter overall sound than he had been known for up to that point, although heavy guitar still features occasionally.  Drummer Anton Fier and bassist Tony Maimone, both of Pere Ubu fame, served as Mould's rhythm section on the album and on the subsequent live shows.  The single "See a Little Light" was a hit on the US Modern Rock chart.

Bob Mould (album): Bob Mould (sometimes referred to as Hubcap) is the third solo album by former Hüsker Dü and Sugar guitarist and singer Bob Mould.  It was recorded and mixed between September & November 1995 and released in April 1996.  Mould played all of the instruments on the album himself, and the sleeve notes declare, "This one is for me."  In the place of traditional band credits, the sleeve states, "Bob Mould is Bob Mould."

Bob Mould: Robert Arthur Mould (born October 16, 1960) is an American musician, principally known for his work as guitarist, vocalist and songwriter for alternative rock bands Hüsker Dü in the 1980s and Sugar in the 1990s.

Candy Apple Grey: Candy Apple Grey is the fifth album by the alternative rock band Hüsker Dü, released in 1986.  It was their first major label album, though Warner Bros. had initially lobbied to release "Flip Your Wig" until the band decided to let SST have it.  "Candy Apple Grey" also marks the completion of the band's transition from hardcore punk to a more well-rounded sonic style which would later come to be known as alternative rock or college rock.  As usual, Bob Mould and Grant Hart individually wrote tracks on the album.  While the band's earlier, more frenetic style is still evident, "Candy Apple Grey" also features more introverted, toned-down material, including a relatively large amount of acoustic guitar.

Hüsker Dü: Hüsker Dü was an American rock band formed in Saint Paul, Minnesota, in 1979.  The band's continual members were guitarist/vocalist Bob Mould, bassist Greg Norton, and drummer/vocalist Grant Hart.  Hüsker Dü first gained notability as a hardcore punk band, later crossing over into alternative rock.  Mould and Hart were the principal songwriters for Hüsker Dü, with Hart's higher-pitched vocals and Mould's baritone taking the lead in alternating songs.

Warehouse: Songs and Stories: Warehouse: Songs and Stories (1987) is the sixth and final studio album by alternative rock band Hüsker Dü, originally released by Warner Bros.  Records as a double album on two vinyl LPs.  The band dissolved following the tour in support of its release, in part due to disagreements between songwriters Bob Mould and Grant Hart over the latter's drug use.  This album, along with "Candy Apple Grey", showcases the increasing maturity of Mould and Hart's writing—a change which alienated some long-time fans.  This album is also known for its battle between the two songwriters, with Mould famously telling Hart that he would never have more than half of the songs on a Hüsker Dü album.

Supporting paragraphs: Bob Mould Hayley Williams
Answer: Robert Arthur Mould