George Racette, an 80-year-old former industrial research and design specialist, is reading about relativity.

"Space and time seem like straightforward ideas," he reads aloud in an even, avuncular voice. "Or so it seemed to everyone until 1905." Racette sits in a soundproof booth, black headset clamped over his ears, a copy of College Physics: A Strategic Approach, open to page 899.

Just outside the booth is his "director," 70-year-old Richard Tave, a former chemical engineer whose task, this morning, is to follow the text while Racette reads, making sure he captures every word of the book - including graphs, photos, captions and marginal notes - accurately.

"There's a photo on this page," continues Racette, while Tave tracks along in his own copy, heavily annotated in pencil. "It's captioned 'turtle with a GPS' and shows a turtle with a harness on it."

Racette and Tave, along with hundreds of volunteers across the country, spent several hours last week turning books - from second-grade social studies workbooks to medical-school anatomy texts - into audio recordings that will be used by the blind or dyslexic.

The national Record-a-Thon, hosted by Recording for the Blind & Dyslexic, marries a timeworn, labor-intensive practice - reading aloud for those who can't read for themselves - with 21st-century technology. Once the books are recorded - a hefty volume such as College Physics can take five months - users can either order CDs from RFB&D's library of 59,000 titles or download them and listen to Clinical Behavior Therapy or When Slavery Was Called Freedom on an iPod.

The 62-year-old RFB&D was founded to record college texts for World War II veterans, blinded or visually impaired from war injuries, to enable them to take advantage of the GI Bill, said Michael Kurdziel, the organization's chief of programs and services.

Now the target audience has changed. More than three-quarters of RFB&D's users are children and adults with dyslexia or other reading disabilities. While just 0.4 percent of the U.S. population is legally blind, dyslexia and other reading disabilities affect as much as 15 percent of the population, according to the National Institutes for Health.

For people whose dyslexia causes them to mix up letters or words, miss suffixes and prefixes, or read slowly and haltingly, "the audio text makes a big difference," says Jo Anne Simon, president of the International Dyslexia Association's New York branch. "It's quicker. And the reader isn't making mistakes. The recorded text is a more accurate representation. So [the listener] is getting the message, which is ultimately the point."

For 9-year-old RJ Taschek of Marlton, the printed word was usually cause for tears. Irene Taschek, who homeschools her son, noticed that he routinely skipped words or lines when he read. Sometimes he reversed letters. She tried borrowing audio versions of children's books from the library, so he could listen while he read, but the narrators spoke too fast, and RJ couldn't keep up.

"We were constantly rewinding the tapes. He became frustrated. I was so concerned about him hating reading. To see him struggling with it broke my heart."

Then another mother told Taschek about RFB&D's audio library, which includes children's classics such as The Boxcar Children and the Harry Potter series along with textbooks. A special playback device allows users to slow down the narration, skip backward or forward easily, or bookmark their place in the text.

"It became a key tool for his reading to improve," says Taschek of her son. "When he was diagnosed with dyslexia at age 7, he was graded at a 1.2 reading level. Twelve months later, he was at 3.5. Now he's almost done his third-grade year and he's reading at a fifth-grade level.

"It's still a struggle for him to read. He struggles with phonics. But there are no longer tears; there's no longer frustration."

Mary McDermott has worked at RFB&D's recording studio in King of Prussia for 17 years. When she started, volunteers recorded books on reel-to-reel tapes; later, they used four-hour cassettes.

Patti Lariccia, 56, remembers those days. She began to lose vision at age 9, due to an eye disorder called uveitis. By high school, she could no longer read print; using a magnifying glass just made the letters blurrier. "I had a great, big, old-time reel-to-reel tape player in my bedroom. It was ancient and cumbersome. The tape would get tangled."

Still, those audio recordings cracked open the world of literature for Lariccia. "I remember listening to Great Expectations and The Great Gatsby. It got me interested in pleasure reading. I started listening to things I didn't have to read for school."

By the time Lariccia was at East Stroudsburg University, majoring in psychology, some of her textbooks were available on cassette. If a professor assigned articles, she paid classmates to read them aloud to her. Today, Lariccia, who lives in Clifton Heights, listens daily to audio books; she favors popular fiction by Lisa Scottoline and James Patterson.

"Now that the digital machines and discs are available, it's a better system," she says. "I usually have at least one book going. I like being able to talk about books with my friends who are fully sighted. It allows you to put some normalcy in your life."

Demand for audio books far outstrips the supply; only about 5 percent of existing titles are available as audio recordings, says Simon of the International Dyslexia Association. That's why she's an enthusiast of new technologies such as text-to-speech: software that can convert written text to a digitized voice.

But Kurdziel and some users of audio books fear something may be lost in that translation. Computer-generated voices, he points out, can't yet capture the nuances of poetry or the inflections of various characters in a Shakespeare play. "There's something very intimate about that human voice being recorded and listened to by thousands of users."

Back at RFB&D's studio, on the first day of the Record-a-Thon, Marcia Zanger takes the director's chair, opening a copy of Fundamentals of Human Resource Management and setting up the computer to record Tave's reading.

Zanger, 77, of Havertown, has volunteered here for 13 years. "Some of the books we read are boring and difficult. Especially the philosophy books" with sentences that meander on for whole paragraphs, she says. "But no matter how boring the book is, you put expression in. You do not read in a monotone."

Tave launches in where the last reader left off - a section on "Separating and Retaining Employees." Zanger stops him with a reminder to include the marginal note; she rewinds a few seconds, and he begins again. "Discharging employees can be very difficult -" he reads in a mellifluous voice.

Recording for the Blind & Dyslexic is always seeking volunteers; after a training session and reading audition, volunteers make a two-hour-a-week commitment for one year. Contact Mary McDermott, 610-265-8090, Ext. 24, or mmcdermott@rfbd.org.