What makes a great composer? Will a computer ever create works that rank among those of Mozart and Beethoven?

Before you answer, listen to these examples of computer compositions and reflect that it was once said machines would never beat us at chess.

David Cope, a composer and professor of music at the University of California, has created a program that analyses the music of masters and then makes its own in their style.

Symphony in the style of Mozart

"That a computer program can produce music like the great composers is remarkable," says Prof Cope. "It tells us something about the roots of musical creativity."

He has used his program, called Experiments in Musical Intelligence, to recreate work in the style of Bach, Mozart, Beethoven, Stravinsky, Joplin and many others.

Looking for patterns, it extracts musical signatures; stylescommon to different compositions by the same composer.

"For the most part, music theorists extract the value of chords. This program examines the way they move in relation to one another," he says.

Chopin by computer

One of its most ambitious compositions has been a symphony in the style of Mozart, which some have called the Austrian composer's 41st. However, David Cope thinks that could be going too far.

So what do people think of synthetic classical music?

Sonata in the style of Beethoven

"They react in a diverse fashion. Many people are intrigued by the possibility that a computer can compose interesting and, at times, emotional music. Others are upset by the fact."

The computer can quantify why Mozart sounds unlike Beethoven or Bach. It suggests the difference between these great composers is more in the detail than first thought.

Computer Rag

David Cope has played human and computer composed music to many people and asked them if they could tell the difference.

"It has fooled many people, including myself. Once I had to take a real example of Bach's music and a computer-generated one to a conference. I took two computer pieces by mistake.

"But quality is in the ear of the beholder. It may be that knowing music is written by a computer will bias people against its merits."

Listening to the computer music, Anthony Pople, Professor of Music at the University of Southampton in England said: "It does sound like music that follows the style of the composer but it does not always do the right thing all the time.

Anthony Pople: It is instant Mozart

"It goes off-track from time to time, it treads water. But it is fun.

"I would probably think it was music by a lesser-known contemporary of Mozart who was not as good."

But is the computer good enough to be considered a composer in its own right and not just a machine that produces poorer variations of the masters?

It is a question that all human composers face. When do they find an original voice?

David Cope: How the program works

David Cope is in no doubt about this issue. "In the elegance of its output I would say the computer has already achieved composer-dom."

Anthony Pople believes computers have a place in the study of music, usually thought of as an essentially human activity.

"If the computer operated at a higher level and got at the essence of musical innovation then it might produce something fresh. Then I would be impressed.

"I think computers are going to tell us about the fundamentals of music over the next 20 years or so."

David Cope says his computer has already written valuable, credible music - a composer in its own right.

"It has convinced me it is a unique composer. Bach and Mozart would have loved it."