Don’t it always seem to go, you don’t find out what you got til it’s gone.

– Joni Mitchell, “Big Yellow Taxi”

ORONO – And it is true. Christopher Zimmerman, conductor of the Bangor Symphony Orchestra, will be leaving to take a position in the too-far-to-commute-from state of Texas. Maestro Zimmerman has accepted an appointment as music director and conductor of the Symphony of Southeast Texas.

“This is an exciting opportunity for Chris,” said BSO President Thomas C. Johnston, “and we wish him well.”

In the meantime, eastern Maine residents have two chances left to see this charismatic conductor in concert with the BSO. The first will be at 3 p.m. this Sunday at the Maine Center for the Arts.

The program is substantial, varied, introspective and extroverted. The compositions include the genteel, the emotional and the idiosyncratic.

In more mundane terms, this concert is like a sandwich, the bread being a pair of Haydn symphonies and the filling, a zesty combination of a Beethoven fugue and an orchestral version of what is probably Shostakovich’s most famous string quartet.

“This is a good program if I say so myself,” said Zimmerman. “We start with a lively and likable Haydn symphony, the Symphony No. 6, also known as the ‘Morning Symphony,’ and we end with another, the Symphony No. 102. While not the best known, it is Haydn at his consummate best. It may not have a nickname, but it is one of the greats. And the fast movement really cooks. It’s full of surprises!”

Zimmerman described the works between the Haydn symphonies.

“The pieces in the middle are the complete opposite. The Beethoven is just barely traceable to the Haydn, but at the other end of the spectrum.”

“Written while the composer was completely deaf, the Grosse Fuge was originally the final movement of Beethoven’s String Quartet in B flat, Op. 130,” said Zimmerman. After Beethoven’s contemporaries heard this movement, “He was seriously accused of being insane! The music now is regarded as at least very profound, if not some of his greatest work.”

Performed only once as the finale of the quartet during the composer’s lifetime, Beethoven was talked into rewriting a different, lighter ending for the quartet, with the original final movement becoming a piece in itself.

The music by Shostakovich was originally a string quartet as well, although the version performed by the BSO will be the fully orchestrated one, called the Chamber Symphony. Says Zimmerman, “He wrote it in about a day and a half on a train, and, ironically, it became his most famous quartet.”

The composer was on his way back from Dresden, Germany, a city that had been devastated during World War II, and the manuscript carries the inscription, “Dedicated to the victims of fascism.”

Zimmerman points out that Shostakovich probably also intended the piece to reflect the conditions of life in the former Soviet Union at that time.

“The Beethoven [piece] might seem like a stream of consciousness, but the Shostakovich is closer to that in reality,” Zimmerman said. “There are some themes, the composer’s initials in German make a kind of recurring motif. And he does quote some earlier works. … It is actually the first piece Shostakovich wrote in which he quotes himself.”

This is a concert that spans the centuries while delivering a range of moods and musical styles, a tasty and substantial musical sandwich to dig your teeth into. And, of course, it will be one of the final appearances of Maestro Zimmerman here in the Bangor area, and so should not be missed.

The Bangor Symphony Orchestra will perform at 3 p.m. Sunday, at the Maine Center for the Arts. For tickets or information, call 942-5555 or 1-800-639-3221.