SOME of history's greatest composers were also virtuoso pianists; Liszt, Rachmaninoff and Chopin are among the better-known examples. But not many composers could also tune, repair, even rebuild a piano.

Michael Harrison, a composer and pianist who lives here and co-owns a restoration company in Irvington, finds as much inspiration in the inside of a piano as in the sheet music that rests above the keyboard.

"The piano has been in a constant state of evolution for 300 years," Mr. Harrison said in a recent interview, explaining that for much of that time, "it was constantly changing and being adapted according to the composers and performers of the day." For the last 125 years, although there have been a few modifications to the piano, it hasn't really changed much.

He added: "I don't believe the piano will remain stagnant. I believe that the piano will continue to evolve as we find composers who have new needs -- such as mine."

To meet those needs, Mr. Harrison has taken matters into his own hands, creating the harmonic piano, which looks like a conventional grand piano but is outfitted with a second set of strings allowing it to play twice the number of notes. He found this capacity essential, he said, because he writes music using an archaic tuning system known as "just intonation," in which the distances between notes are determined by simple mathematical ratios.
Just intonation has roots in ancient Greece, whose theorists determined that all music behaves according to perfect ratios. But around 1700 it gave way to "equal temperament," a mathematically "impure" system that allows modern pianos to be played in all of the keys. Equal temperament is the basis for almost all of Western music today.

Mr. Harrison says he began investigating alternative tunings in the late 1970's while studying Indian classical music with Pandit Pran Nath, a master vocalist who taught him the Indian practice of microtones -- finding the notes in-between the notes. This apprenticeship coincided with Mr. Harrison's classical composition studies at the University of Oregon and later at the Juilliard School. He eventually started to find Western music's 12-note scales too limiting.

"When I started studying with Pandit Pran Nath," he explained, "after the first year or so the piano started sounding out of tune to me because I was hearing the compromises of equal temperament, which I wasn't hearing before." That was the impetus that led him, in 1986, to develop the harmonic piano.

He also began to retune other pianos according to just-intonation properties, and later made a pair of recordings based on these experiments: "In Flight," in 1987, and "From Ancient Worlds," five years later. In 1999 he began his most ambitious work, "Revelation," a 100-minute marathon for solo piano employing an otherworldly vocabulary of sounds and effects.

In a review of a recent performance of "Revelation" by the pianist Joshua Pierce, the Los Angeles Times music critic Mark Swed wrote: "Perhaps the most surprising quality of 'Revelation' is its straightforward sensuality. It has elements of New Age friendliness, along with heaping doses of old-fashioned, jaw-dropping virtuosity that simply pull the listener along."