By JON CARAMANICA


No one paid Patrick Stump much mind during a shopping excursion at the Manhattan vintage vinyl emporium Academy Records early last month. Flipping through racks of albums swiftly, he worked his way methodically through the store, like just another record nerd.

Mr.Stump, 24, prefers it this way. That he is the lead singer of the multiplatinum rock band Fall Out Boy has done little to convince him that attention is something to warm to. Instead Mr.Stump has quite willingly ceded the spotlight, if it was ever on him, to the band’s bass player, Pete Wentz, 29, the rambunctious attention seeker known for marrying the singer Ashlee Simpson, hosting his own show on the cable channel MTV and sharing too much information on the Internet.

In mid-December Fall Out Boy, which also includes the guitarist Joe Trohman and the drummer Andy Hurley, released“Folie a Deux,”its fifth album and third on a major label, Island Def Jam. It’s the band’s most concise, restrained album to date, taking its main cues from slick 1980s arena rock, but what’s notable is Mr.Stump’s growth and versatility, as both a vocalist and a songwriter. The album comes at a time when Mr.Stump is also in increasing demand as a producer for other artists and Mr.Wentz is reconsidering his public image. If there were a time for Mr.Stump to step up and demand notice, this would be it. But if it’s O.K., he’d rather not.

“I never really felt like the frontman type,”Mr.Stump said.“I got really lucky in Pete. He’s such a personality that I don’t have to be a character, really. It’s selfish that I let him get thrust into that, but it was awesome for me.”

Mr.Stump has fronted Fall Out Boy since its inception in 2001 in the Chicago- area punk scene, and he has been the primary architect of the group’s sound, which in short order has evolved from angst-filled anthems to radio-friendly pop-punk. Mr.Wentz, who writes the words, is responsible for the group’s hyperliterate emotional style, but it is Mr.Stump who takes it from there, chiseling Mr.Wentz’s lyrics into traditional song structures, then writing the melodies, hooks and arrangements.

To this day Mr.Stump is modest about his talent. When Mr.Stump auditioned for Fall Out Boy, it was to be the drummer.“I don’t remember ever singing for anybody until I was in a band,”he said.

In recent years Mr.Stump has begun working outside Fall Out Boy, producing for hip-hop musicians and helping to shape songs for other rockers. (He also wrote and directed a short film.) No one seems more pleased with, or relieved by, Mr.Stump’s evolution than Mr.Wentz.“Patrick, I think, is a musical genius. He has a natural grasp of music theory,”Mr.Wentz said.

Whether or not Mr.Stump is prepared to step forward, Mr.Wentz is in retreat. The lyrics on“Folie a Deux”are the least explicitly personal Mr.Wentz has yet written, he said, coming at the time of his highest tabloid value. In May Mr.Wentz married Ms.Simpson, and in November the couple had their first child. This month Mr.Wentz also staged his first art show in Los Angeles.

A couple of weeks after shopping at Academy Records, Mr.Stump was in New York again for the finale of the MTV show“TRL.”Mr.Stump did what he could to savor the moment.

“He was telling me about it,”said Greta Salpeter of the band the Hush Sound,“and he said,‘Oh, man, I had to go be the face and do the celebrity thing. It was terrible!’”