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June 5, 2005
Play
It Again, Vladimir (via Computer)
By
ANNE MIDGETTE
THE
house lights dimmed at the BTI Center for the Performing Arts in Raleigh, N.C.,
one night last month, the stage lights came up on the grand piano, and in front
of a rapt audience Alfred Cortot played Chopin's Prelude in G (Op. 28, No. 3),
as he had not for nearly 80 years.
Cortot is
dead, of course. He was not present in physical form, nor was anyone else
sitting at the keyboard of the Yamaha Disklavier Pro as the keys rose and fell.
But this was his performance come back to life: his gentle touch, his
luminosity, even his mistakes, like the light brush of an extra note at the
periphery of the final chord.
So, at
least, claimed Dr. John Q. Walker, the president of Zenph Studios in Raleigh,
which sponsored the event and created the software that allowed Cortot to
return. Dr. Walker is developing technology that enables him to break down the
sounds of an old recording, digitize them and reproduce them on a Disklavier,
an up-to-the-minute player piano that can record and replay performances by
means of a CD in a slot above the keyboard. Sophisticated fiber optics control
the instrument's hammers.
Old
recordings of great performers are often marred by scratches and surface noise,
or by sound badly filtered through primitive microphones. Dr. Walker is
offering the same music with the immediacy of live performance and the
acoustical advantages of a contemporary piano. To demonstrate the contrast, Dr.
Walker also let the audience at the BTI Center hear the original
Cortot recording from 1926, which sounds as if sand had been poured on the old
disc's shellac.
"The
farther you get from the recordings, the worse they sound," Dr. Walker
said by phone a few days before the concert. "The fundamental root of the
problem is that I don't want to hear a recording. I want to hear the young
Horowitz, Schnabel, Fats Waller, Thelonious Monk on an in-tune piano."
If the
claims he is making for his new technology are accurate, he will soon be able
to. His plan is to approach the major labels with his software and delve into
their back catalogs, acting as a record producer to make old recordings new.
Josef Hoffman without the scratches, Glenn Gould without the mumbling: brought
back to life and performing on modern pianos, recorded with modern technology.
"People
say this is like colorizing old photographs, but it's not," Dr. Walker
said. "This process is like being able to set up the entire scene of that
photograph again and shoot it with a new camera from any angle, forever."
This is
the new world of computer music. In its infancy, way back in the 1960's, the
goal was to use digital technology to create new sounds and new musical forms.
Today scientists around the world are turning computers on human performance,
seeking to quantify an element once thought to be intangible: the expressivity
of a human artist.
The piano
is a good place to start. It offers a relatively limited set of variables. With
the violin, every aspect of sound production is subject to human vagaries: bow
pressure, bow speed, the placement of the fingers. On the piano, it comes down
to hammers hitting strings.
Developed
by Wayne Stahnke, the first Disklaviers were made in the 1980's by
Bösendorfer, the renowned Viennese piano manufacturer. When that company
stopped making them, Yamaha took up the baton, hiring Mr. Stahnke as a
consultant. Mr. Stahnke's best-known Disklavier project was a foretaste of Dr.
Walker's efforts: translations of piano rolls recorded by Sergei Rachmaninoff.
The two resulting CD's of "new" Rachmaninoff performances, both
called "A Window in Time" and released in 1998 and 1999, are still
available from Telarc. Some listeners find these revelatory. Some find them
mechanical, even soulless. The reactions demonstrate a basic difficulty with
mechanical reproduction of music: there is a subjective element involved in
determining if it works. The final criterion for any such reproduction is the
rather imprecise "Turing test" of artificial intelligence: that is,
whether it can make the listener think he or she is hearing a person rather
than a machine.
At the
Austrian Research Institute for Artificial Intelligence, a group of leading
researchers known as the Machine Learning, Data Mining and Intelligent Music
Processing Group are trying to pinpoint just what it is that fools the ear. Led
by Gerhard Widmer, they are looking at everything from improving the way
computers "hear" music to isolating the elements of individual
performance style, as well as creating graphs and animations to illustrate
different pianists' interpretations of the same passage of music.
In a 2003
paper, "In Search of the Horowitz Factor," Dr. Widmer and his team
described giving the computer 13 recordings of Mozart piano sonatas, played
into a Bösendorfer Disklavier by the pianist Roland Batik, to see if they
could use the computer to determine rules that described the pianist's
interpretive choices.
They did
get some rules, though it turned out that many of them applied equally well to
other performances of other music. But the machine generated its own
performance of a Mozart sonata movement that it had not heard Mr. Batik play,
but based on what it had learned of his style. With this, it took second prize
in the International Computer Piano Performance Rendering Contest in Tokyo
in 2002. With no stage fright.
"The
first question was, can we hear Glenn Gould play again?" Dr. Walker said.
"The next question: Cool, can we hear him play other stuff?" To this,
Dr. Widmer might answer: We're getting there.
But
there's still the thorny matter of how to get data from an audio recording into
the computer. It's a question not just of having the computer play back a CD,
but of translating the music into a language the computer can understand.
A
computer, by itself, can't recognize the difference between a note of music and
a cough. It can't pick out a melody from a dense weave of counterpoint. It
can't tap its foot to follow a beat - not, at least, in classical music, where
the tempos are constantly changing. The first problem Dr. Walker faced was how
to get the computer to create a kind of score from the clusters of sounds in a
recording.
"A
recording is sound waves that were sampled by a microphone," he said.
"We feed those into the computer and try to discover what the notes are.
The computer model is a three-dimensional thing: middle C struck in a certain
way looks like a 3-D mountain range. We have a model that looks like math
equations, and we try to fit to it: Yeah, this looks like it's a note."
Dr.
Walker - a trained pianist with a degree in software engineering who sold his
company a few years ago, creating the time and financial flexibility to work on
this project - is coming up with his own answers. But the process is still
extremely time-consuming. He is reluctant to say just how slow it is, but he
has been working for more than three years, and his demo CD includes only a few
tracks: the Cortot, Glenn Gould's performance of the Aria and first variation
of Bach's "Goldberg" Variations, and part of a track by Art Tatum.
Even
after he gets a model that works, Dr. Walker has to contend with the question
of reproduction on a Disklavier: can it mimic human performance down to the
last detail? Dr. Werner Goebl, a member of Dr. Widmer's team in Vienna,
addressed this as co-author of a paper called "Are Computer-Controlled
Pianos a Reliable Tool in Music Performance Research? Recording and
Reproduction Precision of a Yamaha Disklavier Grand Piano." Precisely
measuring the Disklavier's ability to replicate human touch, Dr. Goebl answered
his own question: No.
Less
high-tech but just as relevant are the variations from one piano to another. A
skilled musician compensates for changes in a room or an instrument. A CD
cannot. Dr. Walker encountered one aspect of the problem when he took his
technology to the Yamaha studios to play his Cortot performance for Mei-Ting
Sun, a young concert pianist and the winner of the first Piano-e-Competition in
2002 (judged, in part, via a Disklavier in Japan, which reproduced
performances thousands of miles away for one of the judges).
It had to
do with the final chord in the Chopin prelude - or, rather, with the extra,
wrong note.
"Their
piano wasn't calibrating as ours was," Dr. Walker said, "and the note
didn't sound. Mei-Ting said: 'I know this recording. This wasn't accurate,
because Cortot misses the last chord.' I played it again, and he watched the
keyboard and saw that the key went down but didn't sound. He said, 'O.K., you
guys got it.' "
Mr. Sun
was so convinced that at the North Carolina concert where Dr. Walker's version
of Cortot made his debut, he appeared as the featured live artist: Cortot
played a piece, Glenn Gould played a piece, and Mr. Sun played the rest of the
evening. He had to; Dr. Walker didn't have enough music to fill a whole
recital.
The
technology, in short, is still in its infancy. But Dr. Walker is animated by
his vision of the future. Like other scientists - including Dr. Goebl in Vienna,
another serious classical musician - he envisions a future of interactive
recordings. "We've been trained that a recording is a frozen
document," he said. "Why can't it be like a video game - every time
you hear a recorded performance it's different?" But at the moment, his
focus is on making new recordings in a more conventional manner.
Dr.
Goebl, in Vienna, supports Dr. Walker's work and is interested in
it. But he questions whether it's a "real" performance. (Dr. Walker
is well aware of such skepticism; his response is simply that you can't judge
until you've heard it.) "The timing you can probably get quite
right," Dr. Goebl said. "What is really difficult is to get how long
the notes were held and how the pedal was moved and so on. You don't have that
information. You can just guess. The result is something that sounds like but
never truly will be Gould. It's always an approximation."
So is he
saying that Dr. Walker's track isn't authentic?
"There
you have to go into the philosophical domain," Dr. Goebl replied. "A
recording is just an acoustic document of what took place."
In other
words, a recording isn't authentic, either. It is also at a remove, or two or
three, from the original performer, and it is also affected by the decisions of
the engineers who helped create it.
The Gould
recording, after all, wasn't recorded in one take. Many different takes were
spliced together to create it. Is it any more real than a computer replica?
Only if you say it is.
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