As a child, Shai Shaham of San Francisco loved to gather with his siblings in the family study and listen to his parents play a Beethoven piano-violin sonata.

Music often was the center of even the most mundane family activities. On the way to the store, they played "Name That Musical Note" to tunes on the car radio.

Shaham, now 28, didn't know as a youth what perfect pitch was, much less realize that he had it. So, too, does his brother, virtuoso violinist Gil Shaham, and his sister, concert pianist Orli Shaham. Both were recruited along with Shai for a UCSF study on perfect-pitch perception.

The Jewish family is a textbook case of what genetic researchers suspect is a higher-than-average occurrence of perfect pitch among Ashkenazi Jews. The researchers believe that the trait tends to run in families.

"If you look into the classical ranks, there are a fair number [of Ashkenazim]," said Nelson Freimer, co-leader of the research team. Those thought to have or have had perfect pitch are the late pianist Vladimir Horowitz, the Metropolitan Opera's artistic director James Levine and the San Francisco Symphony's music director, Michael Tilson Thomas.

Those with perfect pitch can call out every note in the alto line of Leonard Bernstein's "Kaddish" without the score, as well as assign notes to nonharmonic tones like the dial tone on the telephone or the hum of a Muni bus, without referring to other tones. While a person with relative pitch can identify an F after hearing a note identified as middle C, those with perfect pitch can identify the F without receiving any clues.

Some individuals are so familiar with the tones, maintains UCSF graduate student Siamak Baharloo, that they associate each one with a specific color, which is a more specialized gift called synesthesia.

An estimated one in every 2,000 people has perfect pitch; among musicians, the rate is 15 percent, according to the researchers.

Baharloo and several others who comprise the research team want to isolate the gene that is partially responsible for perfect pitch. They have grander plans, however, than merely distinguishing the musically inclined from the tone deaf.

The study may be the first to pinpoint a human trait that is both hereditary and learned. That is not to say that perfect pitch is either learned or inherited. The researchers believe that an individual must have both a genetic predisposition and musical training during a critical developmental stage of childhood to acquire it.

Freimer compares the development of perfect pitch to learning to speak.

"We all have the inborn ability to use language skills," Freimer explains. "But if you take a child and cut them off from people until they are 10, it is not likely that they'll learn to speak."

Ashkenazi Jews aren't necessarily more genetically inclined than others to perceiving perfect pitch, he said. But two factors make them good test subjects for this study:

For one, a higher percentage of Jews provide music education to their children at an early age than the general population.

The second test factor is that Western Jews' small gene pool makes it easier to isolate the gene partially responsible for the trait.

While the world's 11.2 million Ashkenazim aren't as homogeneous as they once were, the researchers believe all descended from only a few thousand Jews several centuries ago.

There are other populations — those of Finland and Montreal, for example — with relatively homogeneous gene pools. But they aren't as accessible.

The researchers figured they could find local test subjects among more than 228,000 Bay Area Jews. They need about 100 families for the study.

Statistically, only 114 area Jews should have perfect pitch. The trick will be to find them, Baharloo said.

The Shaham family, which has lived in Israel, is helping the researchers make contact with Israeli Ashkenazim. Individuals in Los Angeles and New York also have been recruited to help.

At UCSF laboratories, Baharloo sits behind a laptop computer that fires 30 tones variously at a test subject. The subject must guess immediately and jot down the corresponding note. The test is designed to weed out those with only relative pitch. More than a couple of wrong guesses fails the test.

Shaham is matter-of-fact about his gift, which he regards as a mere curiosity. Like his sister, he plays the piano. But perfect pitch in no way makes or breaks his career as a molecular biologist. For now, he is content to exercise his pitch in an occasional duet with his clarinetist wife or in other recreational pleasures.