On a warm April afternoon in 2007, the Canadian string band The Duhks were in the middle of a set on the Watson Stage at Merlefest in Wilkesboro. John Paul Jones, Led Zeppelin’s bassist, walked on stage, mandolin in hand, and joined the group for a surprising rendition of “Whole Lotta Love.” Later that night, Jones would sit in with Doc Watson, Earl Scruggs, and the Nitty Gritty Dirt Band in a rollicking jam session.

John Paul Jones was not a scheduled performer; he was there to watch Uncle Earl, a female bluegrass band whose most recent CD he had produced. But his unexpected appearance sums up perfectly the official slogan of Merlefest: “Music. Moments. Memories.”

The festival began in 1988 as a benefit concert to build a memorial garden honoring Eddy Merle Watson, Doc’s recently deceased son and guitar-picking partner. It quickly grew to a weekend-long event. And more than two decades later, Merlefest has expanded into one of the nation’s largest traditional music festivals, routinely drawing more than 70,000 fans over four days to my hometown in the Western North Carolina foothills.

In late April, more than 70 acts will appear on the dozen or so stages scattered across the campus of Wilkes Community College. Most years you can expect to see bluegrass legends, including Del McCoury, Ralph Stanley, and Scruggs; country music standouts such as Emmylou Harris, Jim Lauderdale, Marty Stuart, Lyle Lovett, Randy Travis, and Dolly Parton; newgrass innovators Sam Bush, Jerry Douglas, Allison Krauss, and Tony Rice; and younger acts, including Steep Canyon Rangers, the Carolina Chocolate Drops, Scythian, and Bearfoot.

The uninitiated might think Merlefest is mainly for the lovers of bluegrass, gospel, or traditional country music, but Doc always has called the music he plays “traditional-plus,” and the lineup reflect Doc’s eclectic tastes. Some of the most exciting sets have come from genre-benders like Donna the Buffalo, Taj Majal, the Avett Brothers, Old Crow Medicine Show, and favorite group, the Waybacks. In recent years, Steve Martin, Little Feat, Levon Helm (of The Band), and Elvis Costello have graced the main Watson Stage.

And this year, John Paul Jones’ former bandmate Robert Plant will bring his Band of Joy to close out the festival.

While the music is the main attraction, Merlefest succeeds more than any multiday festival I’ve attended because of the harmonious relationship between the performers, the venues, the audience, and the volunteers. Headlining acts play the Watson Stage, with grounds that can accommodate more than 30,000 listeners. But the smaller stages, both outdoors and inside a few of the buildings, offer a chance to enjoy the music in much more intimate settings. And everyone is welcome to bring an instrument, find an open spot, and pick a little.

Unlike a lot of other festivals, Merlefest is family-friendly. Alcohol is neither sold nor allowed on the grounds. And there are plenty of open and covered areas for kids to play, including a rock-climbing wall and a “Little Pickers” tent for young prodigies, and a dance tent if you want to kick up your heels. Merchandise displays, food and beverage stations, and an Internet café offer places to take a break. Hundreds of volunteers keep the shows on time, the food tents stocked, and the surroundings tidy. And the sound quality is stellar.

Another pleasant surprise is the cost. The festival opens and closes with “short” (seven-hour) days; Friday and Saturday, the music starts at 9:30 a.m. and goes ‘til midnight. Even so, a four-day general admission pass is only $155; a pass with reserved seating for the festival ranges from $225 to $250. And single-day tickets — good for every performance that day — can be had from between $35 and $55. With more than 100 performances at your disposal, Merlefest is a genuine bargain.

What ties the festival together is the presence of Doc Watson, now 88. Doc has cut back his schedule a bit
— the past couple of years he’s performed only two or three days, rather than all four. But he has retained his incomparable voice, crystal-clear playing, and huge heart. Catch him — and Merlefest — while you can.