For celebrated violinist Anne-Sophie Mutter, performing a new work by composer Krzysztof Penderecki is like taking an important musical journey.

"Each time I come back from visiting Penderecki-land," Mutter has said, "I return with a much stronger harmonic understanding and concept of musical colors."

On Saturday (April 29), at London's Barbican Hall, the German

virtuoso presented the world premiere of Penderecki's Sonata for Violin and Piano with pianist Lambert Orkis. The performance followed Mutter's 1999 Grammy

Award-winning recording of the composer's ViolinConcerto No. 2.

While it was Penderecki's idea to write Violin Concerto No. 2 for Mutter, Mutter came to Penderecki requesting Sonata for Violin and Piano.

"At first we were talking about a sonata for solo violin," said the Polish composer from his home in Krakow. "But then I changed my idea and wrote it with piano. I very much wanted to write it for solo violin, but that is extremely difficult, and I think I would need a little more time to do it."

Better Late Than Never

As it stood, Penderecki ran short on time completing the sonata, which was supposed to receive its world premiere in January in New York.

"I finished the piece exactly on the 31st of December," he said, "and this was really late. Anne-Sophie was playing many concerts in Europe at the time, and didn't really have the time to prepare this."

It's no wonder. Clocking in at about 30 minutes, Penderecki's Sonata for Violin and Piano is one of the longest — if not the longest — violin sonatas written by a major composer in the past century, making it a musical trek for Mutter.

"It's extremely difficult and complex, and is rhythmically very complicated," Penderecki said. "So I think it's good that she's had more time now to work on this piece."

The sonata is composed in five movements, with almost half its music contained in the third-movement, Adagio, which is 15 minutes long and is composed of more than 200 bars of music.

"This is, of course, the most important part of the sonata," the composer said. "As is usually the case in my music, the slow movements are the most important."

Penderecki said he thinks of Sonata for Violin and Piano as almost a symphonic work for violin. "The last movement is connected to the third movement, and the beginning music from the first movement comes back in the last movement as well. So this piece has the form of a symphony, really, where in the last movement you have all the subjects from the whole piece come back. In this piece there is really the sum of my knowledge of the violin."

And that's saying a lot, since Penderecki was once a serious student of the instrument. In fact, the composer said that even when writing operas and oratorios, he thinks not in terms of the piano but composes in the voice of the violin.

"I'm really just a frustrated violinist," he said. "I studied violin since I was a boy, and my dream was to be a violinist and to play. So I think that in Anne-Sophie I've found somebody who can play the way I dreamed of playing myself.

"Technically, of course, she is perfect, so there's no limit. Also, she is one of the few violinists who is always looking for new pieces, contemporary pieces, and she really understands this music."

Encompassing A Century

As is the case with many of Penderecki's later pieces, Sonata for Violin and Piano is highly contemporary in style, yet at the same time makes a respectful nod to the past.

"At the end of the last century, many composers were looking back at everything that was important in the century and trying to put it together," Penderecki said. "I was trying to do the same, to write music that has the whole century in it.

"The sonata was finished on the very last day of the year 1999, which is, of course, symbolic to me too. Maybe I was really waiting a bit," he said jokingly, "just to be able to finish it on that day."