A couple of years ago, Shaun Cooper thought his music career was over.

His band, Straylight Run, was falling apart, and the other musician with whom he formed that group, guitarist/vocalist John Nolan, was working on a solo album and seemed intent on following that path.

Cooper announced in a blog to fans that he would be hanging up his bass and retiring from touring.

“I’m not the type of guy that can float from band to band and do this and be totally happy,” Cooper said in a recent phone interview. “I need to be creating music that I love with people that I love, too. And so that just didn’t seem like a viable option at that point.

“I had a lot of friends in bands that I cared about and were making great music, but weren’t also paying the bills too. So I needed all of those things to come together. So really, if one of those needs isn’t being met, I just have to stay home and figure out another job, which I have no idea what that might be.”

Fortunately for Cooper, he never had to figure that out.

Around that time, singer Adam Lazzara, guitarist Eddie Reyes and drummer Mark O’Connell were unhappy with life in Taking Back Sunday, the band they had started in 2001 with Cooper in Nolan.

The latter two had left the band in 2003 and started Straylight Run, which had decent success with its 2004 self-titled debut but had seen its popularity wane before deciding at the start of 2010 to go on an indefinite hiatus.

It was at that point that O’Connell went into action. He reached out (with the approval of Reyes and Lazzara as well as Taking Back Sunday’s management) to ask Nolan about rejoining.

“I was like, ‘I have a question for you. Are you ready for this?”‘ O’Connell recalled in a separate interview. “He was like, ‘Yeah.’ I was like, ‘If we were to ask you to come back into Taking Back Sunday, hypothetically, what would you say?’ And he was like, ‘You know man, yeah, I’d come back and do a reunion show or something like that.’

“I was like ‘No, no come back into the band. Be a member of the band, with an album, tour, the whole thing.’ And he said yeah, he’d be into talking about that at least. So here we are.”

After that, getting Cooper back into the fold was a no-brainer. This restored the lineup that made the 2002 debut “Tell All Your Friends,” which sold more than 300,000 copies and established Taking Back Sunday as a band to watch on the alternative rock scene.

The departures of Nolan and Cooper didn’t derail the band, which went on to make three more studio CDs — “Where You Want to Be,” “Louder Now” and “New Again” — while retaining its popularity. But after welcoming Nolan and Cooper back into the fold, the reunited lineup quickly clicked, and the band released a self-titled studio CD last year.

The album, which peaked at No. 17 on the Billboard 200 and No. 4 on the Billboard Rock Albums chart, suggests that this lineup of Taking Back Sunday still meshes musically. While some key stylistic signatures — such as the blend of sung and screamed vocals and guitar parts that combine aggressive riffing and ringing tones — remain, “Taking Back Sunday” sounds like a step forward for the band and not an attempt to return to the “Tell All Your Friends” era.

That said, the band is taking a look back on its current tour, marking the 10th anniversary of “Tell All Your Friends” by playing that debut album in its entirety. The tour comes to the State Theatre in Portland on Sunday, with Bayside and The Menzingers opening.

“The record is just so important to us,” Cooper said. “We wouldn’t be here without it. We can’t believe that 10 years ago, we put out this record. When we recorded that record and we wrote those songs, all of our dreams were accomplished when we signed the deal with Victory Records and that record was in stores. Like, that was the end of the dream for us. We thought that was as good as it could get.

“So now, 10 years later, being able to play those songs, people still want to hear those songs. A lot of people want to hear them, surprisingly enough to us, and we’re just so grateful we can do it.” 

Alan Sculley is a freelance writer.