A good chorus needs to be versed in French, German and Italian diction. Occasionally Spanish, Russian and Czech come into play.

But Elvish and Dwarvish?

This weekend, local singers will have to master those languages and more as the Pittsburgh Symphony performs "The Lord of the Rings Symphony" under the direction of composer Howard Shore. It's a six-movement work for orchestra, soloists and choruses comprising music he wrote for Peter Jackson's acclaimed film version of J.R.R. Tolkien's 'Rings' trilogy.

"The reason Tolkien invented the languages is because he thought they sounded better," says Shore. "It wasn't just a written-down language. We teach the choirs to sing the languages correctly." Using international phonetic translations prepared by a linguist, adult and child singers are asked to treat the make-believe languages just as they might foreign ones. Of course, it takes extra time to prepare, something Shore is used to by now. "Everything about 'Lord of the Rings' is pretty complicated," he says. "You grow to love it."

Actually, Shore has grown up loving it. The 57-year-old's affinity for Tolkien's books as a boy in Toronto never waned. "It took me 40 years to write 'Lord of the Rings,' if you know what I mean," he says.

As a pre-teen, Shore was already dabbling in composition, eventually leading him to the Berklee School of Music in Boston and a career that spans 60 films including "The Silence of the Lambs," "Philadelphia," "Naked Lunch" and "Gangs of New York."

The "LOTR" symphony was a special project, however. "It was a culmination of what I have done for theater, movies and stage," he says. "It is unlike and surpasses anything I have ever done. I worked on it for close to four years." That amount of time is rare for the movie industry, although it's in keeping with Jackson's extended filming of the trilogy.

Shore looked to 19th-century opera composers such as Wagner for ideas on how to span the sheer length of the films and to create an ambience he felt fit the regal and epic story lines. "Our job was to re-create Tolkien's world as best we could, and Middle-earth is 5,000-6,000 years ago," he says. "I chose the 19th century because it has that classic sense to it, and I looked to opera for architecture of how to build an 11-hour piece. It led to using soloists and choruses -- voices are in the center of the [film score]." The symphony -- reduced to two hours from the film score -- calls for a 100-piece orchestra, a 75-voice mixed choir, a 50-voice boys choir and 10 instrumental and vocal soloists. It has sold out halls in cities from Houston to Antwerp to Taipei in the past few months.

The symphony is programmatic, telling the story of Tolkien's trilogy from the chase of the Ringwraiths to the battle of Helm's Deep. To enhance the experience, illustrations of some of the characters and action will be projected on stage (not scenes from the films, however).

But the music also conveys the interior action of the epic. "Each movie has its own soloists and tried to show the progression of sound," Shore says. "[In the films,] you go from Enya to Isabel Bayrakdarian to Renee Fleming for a transformation of the character, from more of a folk sound to more of an evolved sound. Similarly, there's also a penny whistle in the first movement, in the Shire, but in the last movement [James] Galway is playing the flute. The hobbits have grown up."

As for himself, Shore enjoyed the experience immensely as he pushed himself to complete the film scores and then the symphony. "I think the whole [experience] was a rare thing," he says. "It was a real fellowship making the film, unlike other movies."

The battle for Middle-earth comes to Heinz Hall, Downtown, at 7:30 tonight, tomorrow and Saturday. Tickets are $20-$80; call 412-392-4900.