About 15 years ago, Ellyn Bache read an article about “synesthesia,” a condition in which physical sensations become coupled together — for example, a taste might trigger a visual effect — and she immediately knew she wanted to write about it.

“I thought it was just fascinating. There was a mention of somebody who would hear the broadcast emergency system tone on the radio and just see orange, like an overlay you can see through,” Bache said.

She wrote a short story about it, which was published in Good Housekeeping magazine. On the advice of her editor, she later expanded that piece of short fiction into a novel. The finished product, which was released last month by Harlequin Books, is titled “Raspberry Sherbet Kisses.

” The protagonist of the story, a girl named LilyRose, gets the sensation of raspberry sherbet during a high school kiss. The young synesthete, given her arboreal moniker by her gardener father, feels compelled to hide this strange, rare condition from those around her.

Bache said that, according to the research she’d done for the book, many synesthetes keep their conditions secret for fear of being ridiculed or alienated from friends.

Research at Boston University’s Vision and Cognition Laboratory places the number of synesthetes between one in every 100,000 people and one in every 5,000 people.

The research also suggests that synesthetes are twice as likely to be female and that the most common subtypes are “colorgraphemic, in which letters and/or numbers (and occasionally shapes), produce colors and simple patterns, and color-auditory, in which auditory input, including voices, music and random noise, produces colors, textures and shapes.”

In language, some colloquialisms, such as “loud shirt” or “sour note,” are commonly said to be “synesthetic” terms.

Bache began writing professionally in her 30s when she lived in Maryland. Her children had grown old enough to afford her some free time to hone her skills.

After writing for newspapers, including the Washington Post, she moved into fiction. Her first novel, “Safe Passage,” was made into a film starring Susan Sarandon.

She lived in North Carolina before moving to Souderton a year ago to be closer to her children.

Since arriving, she’s joined a neighborhood reading group, and meets monthly with the Bucks County Romance Writers.

“I’ve been writing almost 30 years, and this has been extremely helpful to me,” she said, adding that members of the writing group are business-savvy and that they expect progress from each other.

“There’s a woman who keeps everybody’s goals: ‘What are you going to do in the next month?’ … It’s just like having a curmudgeonly schoolteacher. It keeps you on track.”

When it comes to local bookstores, Bache cited Harleysville Books as a favorite for its selection and atmosphere, but she added that the Borders Express in the Montgomery Mall surprised her with the eclectic selection and knowledgeable staff that she would expect from a small, independent bookseller.

“Raspberry Sherbet Kisses” can be found in many local and online bookstores.

By Pete Kennedy