Many of us have been listening to guitar-driven popular music for most of our lives. As a result, we’ve unconsciously absorbed the sound of a guitar played in standard tuning, and we can sense when it sounds different. Sarah McQuaid’s guitar playing has that effect. While many guitarists experiment occasionally with alternate tunings, McQuaid plays exclusively in what guitarists call DADGAD tuning; she tunes three of the six strings of her guitars a step lower than standard. This, among other things, gives her music a unified and unique sound. The tuning allows her to play the chords, melodies, and harmonies of the Celtic folk-rock style of her songs while simultaneously accompanying them in drone-like fashion with ringing open strings.

McQuaid was born in Spain, grew up in the U.S., lived for years in Ireland, and now resides in England. You can hear that mix of cultural DNA in her work. Though Spanish influences are not evident, the centrality of the guitar, as in much of Spanish music—a duetting voice rather than mere ­accompaniment—infuses her songs.

McQuaid’s lyrics are thoughtful and thought-provoking. Some of her most memorable songs grow from close observation of small mundane moments, for example, her young son digging a hole in the backyard: “There’s a boy in the garden / with a shovel and a spade.” When that hole becomes rather deep, she warns, “I say I know you’re having fun / I don’t want to make a fuss / but if you dig any deeper / it could get dangerous.” Using Biblical images, she expands that tiny personal moment into an indictment of fracking and the actions of humanity that might result in the destruction of the planet.

McQuaid’s smoky alto—her lowest notes are especially persuasive—invite you to lean in and listen attentively. Though she performs primarily her own songs, McQuaid’s uncommon guitar style and compelling voice also revitalize familiar ones such as Buffalo Springfield’s classic “For What It’s Worth” and Ewan MacColl’s “The First Time Ever I Saw Your Face.”

Now in her early fifties, McQuaid is still climbing toward the zenith of her mastery, but her most recent songs already reflect the wisdom, understanding, and acceptance that comes with maturity. “I am constantly amazed / by the providential nature / of the choices that I didn’t think I made. / Sometimes it’s good to miss the boat. / The ship that sails could fail to float.” 

Sarah McQuaid plays at the Green Wood Coffee House on Friday, September 7.