When John Mayer, Maroon 5 and Jack Johnson hit the road this summer, they'll be singing a green song — and singing it loud.

These artists, along with the Dave Matthews Band and Counting Crows are using their microphones to blast an environmental message during their summer concert tours. But rock 'n' roll 'n' responsibility isn't just what they preach — it's how they roll.    

The acts are opting for biodiesel tour buses and purchasing carbon credits to offset the significant electricity used to light up their stage shows. And they're doing it with the help of Reverb, a nonprofit that aims to get the music industry and eco-community working ... well ... in harmony.

"The music industry has been at the head of many social movements," says Reverb's Brian Allenby, who works with musical acts to custom-green their tours. "Many of our artists also live very environmentally friendly lifestyles, so this is nothing new to the folks we’re working with."

Founded in 2004 by Guster, guitarist and singer Adam Gardner and his wife, environmental activist Lauren Sullivan, Reverb claims to have "greened" over 50 major tours — including those for Linkin Park and the Barenaked Ladies — and kept 35,000 tons of CO2 out of the air.

In addition to helping bands travel more sustainably, Reverb coordinates carpools among concert-going fans, whose commuting typically makes up a whopping 80 percent of a show's carbon footprint. The group also arranges for recycling programs at concert venues, ensures earth-friendly concert T-shirts and sets up "eco-villages" to educate ticket-holders about local and national environmental groups and cool new green technologies.

But they're not the only ones humming this tune. The new Eco-Tunes promises to help artists attain carbon credits, as well as solar-powered stages and sound systems. In Ticketing, seen at Burning Man and Reggae Rising, uses soy ink on hemp/flax tickets and promises "one tree planted per ticket sold."

Reverb's Allenby says all aspects of the industry are starting to hear the music.

"From management companies and artists to labels to promoters to ticket agencies, everyone’s been jumping on board," he says. "Given the size of some of these organizations, it’s not always a lightning-fast transition, but the ground work is starting to be laid, and I truly believe we’ll see some great changes in the next few years."