Punch Brothers fall into a somewhat indefinable category of music. On the surface it sounds like straight-up bluegrass with the banjo, mandolin, fiddle, guitar, upright bass and impeccably tight harmonies. And then there's a drum, which steps outside the boundaries of bluegrass — and that's kind of punk rock, isn't it? Punch Brothers also have one foot firmly planted in classical music, and that seeps into their records and live performances as well. All of these genres collide on the fourth full-length, The Phosphorescent Blues, from the boundary-busting "prog-grass" quintet.

The album vacillates between Beach Boys-esque orchestral-like arrangements under beautiful, tight harmonies, like on the ten-and-a-half-minute album opener, "Familiarity"; to songs that erupt in complete joy like on "I Blew It Off"; to what could be a hip-hop beat in "My Oh My." And a song like "Passepied," the fourth and final movement of Claude Debussy's Suite bergamasque, shows off the boys' classical chops and proves how dynamic an album The Phosphorescent Blues is.

All of these sounds combine to shape a concept album about mobile technology in our lives. Frontman Chris Thile sings about it on "I Blew It Off," which contains lyrics such as, "Your trouble vibrates the table," and "There's nothing to say that couldn't just as well be sent. I've got an American share of 21st-century stress."

During Punch Brothers' in-studio session at The Current, Thile mentioned that this album is his version of The Beach Boys' Smile record. You really hear that. It's not just in the harmonies or the fact that it is a concept record; it's because The Phosphorescent Blues is a timeless collection of songs.