”Girl Group": The phrase commonly conjures images of shellacked bouffant hairdos, fashionably coordinated costumes and close harmonies celebrating romance during the 1950s and ’60s. Hits by the Chantels, the Shirelles, the Supremes, Martha and the Vandellas, the Ronettes and the Shangri-Las indelibly soundtracked teen lives of the era. Later all-female groups from the Emotions and Rick James protégées the Mary Jane Girls through Destiny’s Child and Spice Girls strove to recapture the girl-power magic, but changed the sound considerably.

Then came country boundary-pushers the Dixie Chicks, who changed Nashville trends virtually overnight with their smash 1998 debut “Wide Open Spaces.” The only thing they shared in common with iconic girl groups was chromosomes — and a love of harmony. The Chicks played their own instruments, wrote and chose their own material, and regularly rocked red carpets. They became healthy role models for young girls across the country, encouraging them to pick up guitars and make their own music; they arguably opened the door for Taylor Swift, whose independent image and success has also encouraged girls to express their creativity musically. 

These days there are enough girl groups active just under the mainstream radar that Billboard ran a piece in April declaring girl groups the genre’s “next hot trend.” Not surprisingly, most are more pop than country. But in eyeing the prize of chart success, they seem hellbent on disproving country radio consultant Keith Hill’s infamous admonition that female singers are merely “tomatoes” in modern country music’s “salad.” 

Maybe April, a self-described “country indie folk” trio featured in Billboard’s piece, clearly take a page from the Dixie Chicks playbook. Katy Bishop, Kristen Castro and Alaina Stacey take turns singing lead and sharing spring-clear harmonies, usually with Simi Valley native Castro keeping solid rhythm on mandolin alongside her bandmates’ guitars. Their individual tastes (Brandi Carlile, Kasey Chambers, Iron Maiden, Kacey Musgraves, Chris Stapleton, Keith Urban) merge in a sweet blend. 

Castro met Bishop and Stacey (from Arkansas and Chicago, respectively) in summer 2012 at Grammy music camp in Nashville, where they wrote and performed a song, “Loving You Still.” They relocated to Nashville the following year and have since become semi-regulars at Song Suffragettes, a Monday night showcase for female singer-songwriters at the Listening Room Café. In 2014, they performed “Loving You Still” at a starry Grammy Foundation Legacy at the Wilshire Ebell Theatre. Last year they released a live EP. Next month, they’re opening dates for Brandy Clark and Sarah Jarosz. This week a short California tour brings them to Coffee Gallery Backstage. 

Meanwhile, they’re busily maintaining their social media presence. Their YouTube channel carries their smooth a cappella cover of Beyonce’s “Say My Name” as well as videos of them performing online and onstage, and charmingly goofy roadtrip footage. They’ve covered a lot of miles since music camp.  

Maybe April harmonize at Coffee Gallery Backstage, 2029 N. Lake Ave., Altadena, at 8 p.m. Monday, June 6; $18. Info/reservations: (626) 798-6236. Maybeapril.com, coffeegallery.com