During Detroit Symphony Orchestra practice sessions, conductor Antal Dorati waits silently as his musicians take time out for an unusual preperformance ritual.

Before the up beat, the assistant bass fiddle player passes out free samples of his own product, Mack's Pillow Soft Earplugs, to several of his artistic colleagues, usually making a lengthy stop at the brass section in front of the drums. Unceremoniously, the musicians insert their earplugs.

Earplugs? For master producers of sound?

This isn't the Twilight Zone. It's the story of what one family calls its "fabulous adventure."

Manufactured and marketed by Ray Benner, a former Washington resident and exprincipal bass fiddle of the National Symphony Orchestra, Mack's Pillow Soft Earplugs have earned high accolades from ear, nose and throat doctors, swimmers, construction workers and others who have searched for a comfortable, reusable and convenient form of hearing protection.

And, not incidentally, they have made Ray Benner if not rich, rather comfortable.

"Most musicians supplement their incomes with music instruction," the accidental entrepreneur says. "But I've always been one to look for new ideas.Curiousity led me into this business back in 1962."

That's the year Benner spotted an advertisement placed by an elderly pharmacist who wanted to sell his earplug business. The cost was $2,000, and the business was said to produce $1,400 in additional income annually.

Benner's wife, a bookkeeper, liked the challenge, so a deal was struck to purchase the company, McKenon Products Inc. of pleasant Ridge, Mich. "Had we known more we probably wouldn't have done it," Benner recalls. "Our naivete was in our favor. It's been a fabulous adventure."

Under the Benners' guidance, that adventure has grown into a cottage industry -- actually in the Benners' basement -- that grosses about $750,000 a year. The entire Benner family helps produce Mack's Pillow Soft Earplugs in their spare time, and the business provides employment for about a dozen eager and well-paid teen-agers.

Last year alone, the business grew 95 percent in volume, and even in the weakest years, Benner claims at least 15 to 20 percent annual growth. His neighborhood industrial force manufactures about one million sets of earplugs each year.

The big break for Mack's came about six years ago when the earplugs were featured in an article in a major medical journal. The publicity resulted in an order from the Thrift Drug Store chain for about 600 dozen sets.

"We were astounded," Benner says. "We had never seen anything like it!" The family worked overtime to fill the order, and Benner requested a list from the chain of stores carrying his product. He then started sending samples out to other drug store chains and ear, nose and throat doctors. The response was overwhelming, and Mack's earplugs are marketed nationwide.

"I have the best sales force in the country -- ear, nose and throat doctors," brags Benner, "but our success has not been without problems."

The biggest problem, he says with a laugh, is that his family had to move into a larger house with a bigger basement to keep up with the expanding business.