Linda Perhacs' story sounds like the plot for a Hollywood movie: Dental hygienist who writes songs in her spare time is discovered by a music biz bigwig while she cleans his teeth. She makes a brilliant album that sells zilch, and drops out of the music industry. Decades later, record collectors and freak folkies rediscover the album, and it's reissued without the songwriter's knowledge. Eventually the visionary hygienist is found, and learns she has an audience. If this were a movie, the scenario would likely end with the vocalist playing for a sold-out crowd at Carnegie Hall after her new album became a hit, though that hasn't happened in real life yet. Still, the fact that Perhacs has returned to duty and is creating compelling new music 47 years after her cult classic Parallelograms came and went is more than remarkable in itself. At the age of 74, Perhacs has released her third album, 2017's I'm a Harmony, and the passing of nearly half a century has made a difference, though not as much as you might think. Perhacs' voice is more fragile and whispery than it was in 1970, and she doesn't hit the notes as reliably as she once did. That said, her instrument is surprisingly functional given how long she avoided singing in public, and the many collaborators who help her on I'm a Harmony are both generous and knowing in their musical and vocal support. (Significantly, the cover reads "The Voice and Vision of Linda Perhacs" before listing the artists who pitched in to help make the album a reality.) As a songwriter, Perhacs' muse has barely aged a day, and the playful but heartfelt hippie-style visions and soaring melodies that dominated Parallelograms are still here in abundance; if the craft here feels more 21st century, the heart and soul are very much the same, and Perhacs has remained loyal to the musical vision she first documented in 1970. And Perhacs' partners on I'm a Harmony serve her very well; the album was produced by Pat Sansone (of Wilco and the Autumn Defense) and Fernando Perdomo in collaboration with Perhacs, with appearances from Julia Holter, Devendra Banhart, Nels Cline, and Mark Pritchard, and the results are graceful and powerfully atmospheric, individual while flattering the style of the headliner. I'm a Harmony isn't the revelation that Parallelograms was, but it's not a letdown, either; this is the work of an artist whose singular creative viewpoint hasn't dimmed with time. She still has a great deal to say, and those who loved her debut will discover she hasn't lost her touch.