A 15-minute piece of music reconstructed from fragments Beethoven wrote for a 10th Symphony that he never finished received mixed reviews Wednesday from critics.

The piece was the result of five years' work by Barry Cooper, a researcher at Aberdeen University in Scotland. Played by Britain's Royal Liverpool Philharmonic Orchestra and conducted by Walter Weller, it had its public premiere Tuesday night at a concert at London's Royal Festival Hall.Edward Greenfield, writing in the London newspaper The Guardian, wrote: "Though even Dr. Cooper would never assert that it was what Beethoven would finally have delivered . . . I marvel that the long Andante sections which framed this unexpectedly structured movement are so genuinely Beethovenian."

Paul Griffiths of The Times of London wrote: "Proper judgment of how Dr. Barry Cooper has interpreted Beethoven's presumed sketches for a presumed Tenth Symphony will have to await publication of the score: his statement that `about two-thirds of it is based directly on Beethoven's sketches' begs an awful lot of questions, especially when we are concerned with a composer of such notoriously untidy working habits."

Anthony Payne wrote in another London paper, The Independent: "The audience was only mildly enthusiastic. In truth, the music sounded half-formed."

Payne added: "There has always been speculation about sketches for a Tenth Symphony. Until the mid-1980s, however, no scholar had been prepared to identify much material from the 8,000 or so pages of sketches which Beethoven left at his death (in 1827) as possibly relating to the mythical Tenth."

Violinist Sir Yehudi Menuhin, who conducted the second half of the concert after the piece was played, said: "I think it is a valuable work. It is certainly Beethoven. I have huge admiration and respect for Dr. Cooper, who has done an extremely good job."

Cooper told reporters the years researching the musical mystery uncovered sketches that "struck me as being particularly good, even by Beethoven's standards."

He said Beethoven's plans to finish the symphony were mentioned in a letter written eight days before his death. "He actually offered it to the Royal Philharmonic Society" of Britain, Cooper said, "and now they've got it, or as much as there is of it."

Cooper added, "I think the overall result has got enough really good Beethoven in it to make it very well worth hearing."