Constantine Maroulis
David J Dowling/Reflex
"We've been through so much together, from Rent to American Idol," says Maroulis. "With all of my solo projects speeding up, we just felt it was time to move on."
Maroulis, 30, has started work on a solo album and has a development deal to star in an ABC sitcom.
Before he leapt to fame on Idol last year, the singer toured with Rent in 2003 and fronted hard-rockers Pray for the Soul of Betty.
His turn on the reality competition boosted the group's profile and led to increased sales of their self-titled CD, though not enough to make them multi-platinum-selling stars.
Maroulis, who finished sixth on Idol, told PEOPLE last year that not winning the competition was the "best thing that's ever happened to me. I'm not cursed with that stigma of being the American Idol."
