Concerts always fluctuate around beginnings and endings in the strictest musical sense. But the Pittsburgh Symphony Orchestra's current series featured the local premiere and introduction to Ralph Vaughn Williams' Symphony No. 4, a rare occurrence here in the United States, even though the piece was composed in 1935.

It was conducted by Yan Pascal Tortelier, who is finishing up his PSO contract as principal guest conductor. Leonard Slatkin will assume that post next year, although Tortelier will be back as one of a small army of guest conductors.

Those who have heard Vaughan Williams' work have likely not heard anything like this bombastic and dissonant piece by the generally meditative and folksy British composer. Some have said it reflected his humor and "poisonous temper"; others said that it offered a prelude to World War II, the path chosen by Tortelier.

Often deliriously cinematic in content with its overlapping thematic elements, Vaughan Williams' symphony was relentlessly aggressive and occasionally austere, but certainly worth a hearing, particularly in the mocking subtext of the third movement, which took full advantage of a crisp attack from the wind sections, and the fourth movement, which marshaled the PSO's considerable forces.

Be prepared for an explanatory introduction by Tortelier, with PSO resident conductor Daniel Meyers conducting the musical fragments. More entertaining than most with Tortelier's dramatic delivery, this young and old persons' guide to the orchestra should be relegated to a pre-concert talk for those who avoid the program notes.

In the concert's other work, soloist Horatio Gutierrez was nothing if not authoritative from his opening cadenzas in Beethoven's fifth piano concerto, highlighting the clarity of the score's vision, but unfortunately heavy-handed on the poetic side of the scale.

It wasn't until the transition into the third movement, so tender and wonderful, where he began to gather steam. The final section had it all -- a delicacy contrasting the power and silky runs providing the impetus to the end.

The program will be repeated tonight and tomorrow at 8 p.m. Call 412-392-4900.