Here's something I prepared earlier

Just sitting down and playing the piano wasn't enough for the composer John Cage. He used everything at his disposal to turn the instrument into a hardware store. Is there a future for this musical transformation?

The Victorian poet Leigh Hunt once described the piano as "a harp in a box". With the American composer John Cage, the expressive potential of both harp and box was extended through the placing of various objects - mainly bolts, screws and rubber bands - between the piano's strings to create the "prepared piano".

"The result is a gamut of sounds moving from lower to higher octaves without the correspondences of pitch characteristic of scales and modes," Cage wrote in a set of notes to accompany his "Table of Preparations" for the Sonatas and Interludes of 1946-48, his masterpiece of the prepared piano form. "These sounds are of different timbres and of a decibel range comparable to that of the harpsichord. In effect, the prepared piano is a percussion ensemble under the control of a single player."

Cage's compositions for prepared piano, of which he wrote a number during the 1940s, are perhaps the most approachable and successful of all his many works, and the Sonatas and Interludes are now almost popular, having been recorded several times.

The magical combination of sounds in these pieces evokes a mysterious, dream-like world, as if a child was playing with the springs and chimes in the innards of an old grandfather clock. But their lightness of texture belies what was a stormy period in Cage's life. As suggested by the title of one of the earliest pieces, The Perilous Night (named after an Irish folktale collected by Joseph Campbell), this was Cage's own long, dark night of the soul.

During the years of the prepared piano compositions, Cage had an identity crisis. He separated from his wife Xenia, who was also a musical partner, and began his long relationship with the choreographer Merce Cunningham. After an abortive Jungian analysis, he then started to investigate the various sources of Eastern philosophy that were to occupy him for the rest of his life. It was also a time of accelerated change in his music, in which - however hackneyed it sounds - Cage first found his own voice as a composer.

The summary of the period in David Revill's 1992 biography fairly flies along. On a 1949 trip to Paris, Cage conducted research into the music of Erik Satie, and met Pierre Boulez and Pierre Schaeffer, one of the inventors of musique concrÿte.

At the invitation of Messiaen, he demonstrated the prepared piano to a class at the Conservatoire. Shortly after his return to New York, he met Morton Feldman for the first time, who introduced him to the pianist David Tudor, his key collaborator on the infamous - and silent - 4'33" in 1952. In 1951, Cage began to attend the lectures on Zen by DT Suzuki at Columbia University, which led him to the avoidance of "intention" in his subsequent methods of composition. What might be called "the prepared piano years" seems, therefore, essential to an understanding of Cage the composer. Last week, an exquisite new recording of two related works from this period, the Concerto for Prepared Piano and Chamber Orchestra of 1950/51 and Suite for Toy Piano of 1948 (in both solo and orchestrated versions), is released as part of a Cage disc on the ECM label. The album is entitled The Seasons, after Cage's first orchestral work, but it is most notable for the piano pieces, which are played by Margaret Leng Tan, a specialist in the preparation of the prepared piano.

"I was interested in stepping repertoire away from the normal concert and putting together a programme of Western composers influenced by Asian attitudes," said Tan when I met her last month at the Whitney Museum Sculpture Court in New York. "John Cage heard me play a couple of his early piano works and he was very taken by the way I prepared the piano, because you can prepare it very badly.

"In the early days John Cage tried to control the results by making incredibly complex instructions for the preparation of the piano, to the 15th or 16th of an inch, as part of his overall pattern of control," says Tan, banging a screw down on the table by way of illustration. "But the length of strings varies on different pianos, and what worked on a six-foot piano wouldn't work on a nine-foot concert grand. Because I'm from the East [Tan was born in Singapore, and moved to New York to study at the Julliard School at the age of 16], this gave me a critical instinct about how to prepare the piano. This is why John Cage was impressed."

Tan had a working relationship with Cage for the last 11 years of his life, and she was with him on the day before he died in 1992. When she asked if she might ignore his incredibly detailed instructions for two early pieces she was planning to perform, Cage said: "I'm so glad you said that." The urge to control every aspect of performance was something that the later, non-intentional Cage was evidently happy to give up, as part of his philosophical "letting go".

Tan is meticulous about her preparations and their disassembly, as concert venues are understandably sensitive about the presence of a rogue bolt in the Steinway. "Like a good girl scout, I always leave a campsite tidier than when I found it. I also like to be asked back. Steinway gives me their 'Good Housekeeping' seal of approval."

Cage's materials for the preparation of the piano reflected his environment, and finding equivalents for 1940s DIY stand-bys is not always easy today. "He used everything from supermarket mushroom containers, transparent chocolate box wrappers, even the plastic covers from chequebooks," Tan says. "It was the whole found-object principle, like Picasso."

To compensate for changing fashions in DIY, Tan has had to improvise; the consistency of rubber bands has evidently changed considerably, and she is sometimes pressed into using condoms as replacements. "I drive the local hardware store crazy," she says. "Where do you get a stove-bolt these days?"

For Tan, who has written a paper on "Eastern Influences on John Cage", Cage's use of silence as a compositional tool is not, as it is sometimes considered, a Dadaist, Duchampian stunt, but part of a serious involvement with oriental philosophy. "In Western music, silence is a no-no. In Cage, are the silences simply the white spaces between the sound-events, or do the sounds interrupt the expanse of silence, just as in calligraphy the black ink is an interruption of the paper's whiteness? There are those who feel Cage's ideas are so momentous and far-reaching that they will in the end surpass his music. I disagree, because I think some of the works from the Forties are among the pinnacles of the 20th century."

'John Cage: The Seasons' is released on Monday by ECM. Margaret Leng Tan makes her British debut at the Wigmore Hall in March next year, as part of 'Evelyn Glennie and Friends'. A double CD of Cage's text pieces, 'John Cage Reads Cage', is also released this month on Mode, distributed by harmonia mundi