After services at Temple Adath Israel have concluded, after its staff has long left for the night, the fluorescent lights in a back room of the Merion worship center flicker back to life.

Inside the community room, on this Tuesday like so many others, an unlikely group of doctors, mothers, car mechanics, and lawyers gathers, keyboards, and cymbals, and violins in tow, and waits.

Meanwhile, at a Bala Cynwyd Starbucks, music director Reuben Blundell thumbs through his sheet music one final time, scribbling last-minute notes in the margins. After a final sip of coffee, he packs his briefcase and begins his weekly half-mile trek to the group awaiting his arrival.

Blundell and these 80 or so musicians make up one of Delaware County's little-known gems. They are members of the Lansdowne Symphony Orchestra, preparing for Sunday's first concert of 2016. It will be a special one: The symphony will celebrate its 70th anniversary.

Humble but talented, relaxed but passionate, the musicians gather weekly to practice for hours.

This group is not to be confused with the Philadelphia Orchestra. The Lansdowne Symphony consists purely of volunteers. Its operating budget is sparse. And it, like symphonies around the region and the nation, is fighting to survive in a musical field that by many measures has been leaking popularity.

Concert attendance has slipped, as have sales of classical recordings. Last year, classical commanded just 1.3 percent of music consumed in the United States, according to a Nielsen survey, compared with 24.5 percent for rock.

Yet that doesn't matter to the Lansdowne Symphony's musicians. Balancing full-time jobs and children, obligations and busy lives, the members - from both sides of the Delaware River - are part of a long tradition. Lansdowne's musicians have been meeting almost every week for seven decades.

"We're here because we love it, because we get to play these great pieces that are left behind for us," said Blundell.

Community symphonies in particular have confronted challenges. With paltry budgets and an aging concertgoing demographic, they have struggled to bring in new revenue and audiences - and many nationally have had to shut down.

Nevertheless, the Philadelphia region boasts a robust volunteer symphony scene, with multiple orchestras for various age groups and skill levels.

Lansdowne's symphony operates with an annual budget of $50,000, said Robert White, a member of the board of directors. That covers expenses related to the five annual concerts at the Upper Darby Performing Arts Center, as well as Blundell's salary.

Blundell, 35, joined the symphony last year. An Australian violinist turned conductor and a self-described "freak who has never stopped loving classical music," Blundell travels from New York City each week by train for the rehearsals.

The commute is worth it, he said, adding that he regards the Lansdowne Symphony as one of the region's best.

"The level of commitment is incredible," Blundell said. "These are people who work full-time jobs" but still come to rehearsal having already practiced the music.

Blundell, the symphony's fourth conductor, leads without a heavy hand. As smooth, rich notes emerge, he bounces and sways, so that as the music crescendos, it appears to flow off of him. At the end of a piece, he's quick to compliment - and even quicker to crack a joke.

"Anyone recognize this?" he asked this month as he directed the musicians to a new piece of music. "As comedian Amy Poehler said, 'I think it's from this little indie film called Star Wars.' "

Each rehearsal features an eclectic mix, sometimes the classical greats or pop-culture favorites. With each, Blundell said, he tries to induce something new and challenging.

At Sunday's 3 p.m. concert at the center on Lansdowne Avenue, the symphony is slated to play Mozart's Serenade No. 10 ("Gran Partita") and Rachmaninoff's Symphony No. 2. Tickets are $18.

The symphony will hold a pops concert in April.

Herold Klein, the concertmaster and first violinist, has played with the symphony for 20 years. Even after a career with the Philadelphia Orchestra spanning four decades and a stint with the Army's Strolling Strings, he said, there's something rare about Lansdowne's group.

"It's serious soul satisfaction," Klein said. "These people . . . have a thirst for being able to participate in the music."

And that, he said, can't be found everywhere.

610-313-8113 @mccabe_caitlin