Joyful, joyful was the sound of the Bangor Symphony Orchestra Saturday when it gave the first of two concerts this weekend at the Maine Center for the Arts.

There was much to be joyful about.

The BSO, which calls itself the longest continuously running orchestra in the nation, turned 100 this year. It has matured under many impressive batons, the history of which is traced in a newly released, BSO-produced book. But probably none of the conductors has been as ambitious as Christopher Zimmerman, the current music director of the symphony.

Under Zimmerman, who stepped into the position two years ago, the BSO has taken an important step toward sophistication and away from a parochialism that was already waning under its previous director, Werner Torkanowsky. Zimmerman has insisted on technical sharpness in performance and a progressive attitude in programming.

Naturally, there’s still room for growth, and one senses there are more tricks up this symphony’s sleeve. In the meantime, Zimmerman’s vision and the musicians’ hard work and talent have produced a BSO that is growing at a splendid pace and entertains with unprecedented skill.

In the last of this season’s classical concerts, Zimmerman led the BSO and nearly 200 singers from the University of Maine Oratorio Society and University Singers in booming performances of Giuseppe Verdi’s “Te Deum” and Ludwig van Beethoven’s “Symphony No. 9 in D Minor (Choral), Op. 125.”

The Verdi piece, which lasted about 15 minutes, teased the audience with chilling strains and glorious volume. “Te Deum” was not the particular draw of the program; the 9th was the element that sold out both the Saturday and Sunday concerts. But the Verdi was a nugget of gold, and the singers were actually at their shining best in this theatrical and sacred piece.

One always worries when an amateur group takes on something as massive and as dear to music lovers as Beethoven’s 9th. But there was no need for anxiety. Both the BSO and the university performers, who had been rehearsed under music Professors Ludlow Hallman and Dennis Cox, were up for the task.

On Saturday, the opening movement was proficient but lackluster. What followed, however, was a forcibly restrained second movement. The pacing — another of Zimmerman’s fortes — flew with spirit, humor and well-defined choices. It was smart and dynamic, and perhaps the most interesting of the four movements.

The third movement had an epic quality, but it was the last movement that the audience came to hear. With a full orchestra, nearly 200 singers onstage and four soloists (Meredith Harewood, Melissa Malde, Stuart Skelton and Michael Kavalhuna, all of whom have affiliations with College-Conservatory of Music in Cincinnati where Zimmerman teaches), the Maine Center was wild with sound.

If a solo instrument was sometimes wobbly, or if the fullness of the voices slipped over the top of listenableness, it didn’t matter. The overall effect was astoundingly bright and smart, and the audience hung on every unleashed note in this finale.

It was a grand end to a season that flowed with success. And a clear indication of what can be expected next autumn when the classical concerts begin the 101st season of this remarkable community symphony.