Actor Peter Ustinov, whose roles have ranged from Babar the Elephant to Rome's mad emperor Nero, is now playing Beethoven's ghost before packed houses in West Berlin.

The play, "Beethoven's Tenth," was written by Ustinov and has been performed in the United States and in Britain. However, its West Berlin debut at the Schiller Theater marks the first time Ustinov has delivered his lines in German.Ustinov, who turned 67 on April 16, admits that speaking German is his biggest challenge in the performance.

"For me, every night at the Schiller is a premiere," he said in a recent interview. "German is a difficult language. It forces me to attempt linguistic acrobatics with my mouth that I'm not used too; I'm constantly in danger of getting stuck."

For the interview, Ustinov made his remarks in nearly fluent but cautiously enunciated German.

The play opened in West Berlin in January and has been sold out ever since. More than 40,000 people are expected to see the production before its scheduled April 30 closing, Gisela Huwe, a theater spokeswoman, said.

"`Beethoven's Tenth' is one of the greatest successes in the 40-year history of the Schiller," Huwe said of the two-act play written by Ustinov.

Much of the play's action concentrates on efforts by a fictional London music critic named Stephen Winter to imagine how Beethoven's 10th Symphony might have sounded. It also focuses on his often stormy relations with his son, Pascal, who composes modern symphonies which Winter has no use for.

A Viennese au-pair girl named Irmgard, who loves Beethoven and Pascal, manages to wake the composer from the dead. The composer rings the doorbell and strides, with long hair flowing, across the stage.

With the help of a hearing aid provided by the family doctor, the old deaf master is able to hear his symphonies for the first time.

Ludwig van Beethoven's last completed symphony is his ninth The Choral. Music researchers, however, say they have discovered sketches for an unfinished symphony, possibly a 10th, dated after completion of his Ninth Symphony and before his death in 1827.

In Ustinov's play, the audience never learns how the 10th Symphony really sounded, but the resurrected genius helps bring the feuding Winter family closer together.

Critics say Ustinov's often deliberate German delivery adds to the performance, increasing audience empathy to the character of Beethoven, who makes a grumpy visit to the 20th century in a rumpled coat and wig after 160 years in the grave.

Ustinov said he especially enjoys playing on the West Berlin stage.

"The actor is in direct contact with the audience here," he said. "The people are very warmhearted."

Ustinov is internationally known for his versatility as a stage and screen actor, and in recent years has become best known for his portrayal of Agatha Christie's Belgian sleuth Hercule Poirot.

He has written several other plays, a collection of short stories and a novel.

In film, he gained prominence for his portrayal of Nero in Mervyn Le Roy's 1951 Hollywood epic, "Quo Vadis."