For its 18th edition, Springfest, the annual cornucopia of Americana, bluegrass and roots music in woodsy, moss-festooned Spirit of the Suwannee Music Park, seemed to attract a larger group of younger listeners than in previous years. At least, that’s what it felt like when festival favorites the Avett Brothers – who impressed Live Oak crowds long before Scott and Seth ascended to arena tours – packed the Amphitheater for two hours’ worth of stomping acoustic-electric music that had fans pushing to the front and singing along with every word of every song.

The North Carolina-born siblings and their four bandmates again demonstrated infectious high-energy joie de vivre, showcasing some material from the last two years’ “Magpie and the Dandelion” and “The Carpenter” releases. They also turned in stirring versions of the title track from “I and Love and You” and that 2009 album’s “Kick Drum Heart” and “Laundry Room,” as well as a moving “Amazing Grace.” There were also rowdy covers of Lefty Frizzell’s “If You’ve Got the Money I’ve Got the Time,” John Denver’s “Thank God I’m a Country Boy” and traditional mountain song “Old Joe Clark” – the last two with a little help from Sam Bush, on fiddle.

The old guard and the younger crowd, though, on stage and off, handily mixed and matched in nearly 70 performances spread across four stages, with some acts playing twice. The Punch Brothers, whose leader, singer and mandolin wizard Chris Thile, has played the fest with Nickel Creek, turned in another of the weekend’s most impressive performances. The quintet excelled with airtight multipart harmonies, imaginative arrangements and locked-in acoustic synchronicity on “This Girl,” “New York City,” Seldom Scene favorite “Through the Bottom of the Glass,” a Debussy piece and, on the encore, a stunning, extended a cappella version of Dominic Behan’s “The Auld Triangle.”

This year’s Springfest was rangier than in the past, with a program encompassing the top-shelf bluegrass of Steep Canyon Rangers; the stomping country rock of Willie Sugarcapps, featuring singers-songwriters-instrumentalists Will Kimbrough and Grayson Capps; the laidback grooves of fest favorites Donna the Buffalo; the jaw-dropping mandolin work of Sam Bush, and his covers of Stevie Wonder, the Rolling Stones, and Little Feat; and the songwriting brilliance and rugged twang-edged roots rock of Jason Isbell. Isbell’s bracing set included “Decoration Day,” “Traveling Alone,” “Stockholm,” and “Cover Me Up,” and shut down with a slamming “Super 8.”

Also making strong impressions were Tallahassee family group The New ‘76ers, featuring the Southern-fried soulful singing of Kelly Goddard; Asheville, N.C. newfangled string band Town Mountain, which dipped into jamgrass; Greensboro, N.C.’s Holy Ghost Tent Revival, its brass-edged rock ‘n’ roll played by young musicians perpetually in motion; prolific singer-songwriter Jim Lauderdale; and Beartoe, with the Central Florida group’s three female backup singers echoing and engaging in call-and-response with front man Beartoe Aguilar on swampy blues and gospel-tinted rave-ups.