EVERETT — After failing to raise $3.5 million in a capital campaign and suffering through a weakening economy and rising rental rates, the struggling Everett Symphony Orchestra has sold its showcase building on Colby Avenue, the symphony board announced Friday.

The name of the local buyer won’t be made public until the sale on the art deco-inspired building at 2710 Colby Ave. is finalized at the end of August. Under terms of the pending agreement, the symphony will lease the building for two years for about $8,000 a month.

During those two years, the symphony will begin the process of moving to its future permanent home at the Historic Everett Theatre, a bit farther south, at 2911 Colby Ave.

Beginning in the fall, the symphony will play some of its concerts at the Everett theater. The plan is that the symphony will play all its concerts at the theater by the 2009-10 season.

Though the symphony will rehearse and perform at the 107-year-old theater, it won’t have offices there. So these two years will also provide some time for the organization to find smaller yet suitable office space.

“We have two years to ­transition and that gives us breathing room to find the perfect space for our organization and to consider all our options and the needs of our patrons, volunteers, staff and board,” ESO board president Myrna Overstreet said.

The symphony began a capital campaign to raise $3.5 million in early 2000, with hopes of buying its building after it was transformed from three retail spaces into ESO’s administrative offices. But the $3.5 million goal was never achieved and the symphony had to continue paying a mortgage along with other overhead costs, said ESO executive director Jody Matthews.

In addition to those expenses, the symphony has felt the pressure of rising costs of renting the Everett Civic Auditorium where it typically performs. The Everett School District, which owns the auditorium, doubled the rental rates last year. That caused the symphony to discontinue its children’s concert program at the auditorium and also forced it to look at other performance venues.

Over the years, Idamae Schack and her late husband, John, gave millions of dollars to both the Everett Symphony Orchestra and the Historic Everett Theatre. Recently, Idamae and her stepson, Jim Schack, decided the two groups should join forces with the goal of becoming stronger and surviving longer as partners.

The partnership was created when Idamae and Jim Schack transferred the note they held on the Everett theater building to the symphony. The theater building is worth about $2.5 million.

That partnership will now create a permanent place for the symphony to play, reduce rental costs for the symphony and provide a more flexible schedule for their performances, Matthews said. And getting out from under the mortgage saves the symphony between $3,000 and $5,000 a month, she added.

“It’s a really good marriage,” Matthews said.

Though some donors are disappointed about losing such a pretty building, Matthews said she has told them that selling the building is the responsible thing to do.

“We’re making the decision for the economic health of this organization,” Matthews said.

Another plus for the symphony is the prospect of performing to a full house at historic Everett, which seats 834. The Everett Civic Auditorium, at 2415 Colby Ave., seats more than 1,500.

This year, the symphony plans to perform its popular series at the Everett theater, which includes light classics, the Boston Pops concert and some jazz.

The hope is that the symphony concerts will become so popular that the symphony will have to expand into two performances for each concert — a matinee and an evening show.

“We’ve been struggling like every other arts organization and that’s nothing new. It’s part of being a nonprofit, but it does get wearing and it would be nice to get ourselves on some good footing that maybe will bring us some more sustainibility,” Matthews said.

“The goal of this is that all the musicians ever have to worry about is going on stage and setting up their instruments and playing and they never even have to think about another thing,” she said. “They know their paycheck is going to be there, they know they have the support from the staff, the schedule is there and their contract is there.”

Reporter Theresa Goffredo: 425-339-3424 or goffredo@heraldnet.com.