She was a composer who wrote scores with geometric shapes, a poet who became a pioneer of early electronic music. Joanna Brouk’s body of work exists at the nexus between ambient, new age, drone, and classical minimalism—stark in its simplicity, lush in its expanse. Studying under Robert Ashley and Terry Riley at the fabled Mills College Center For Contemporary Music before graduating into the margins of the ’70s Bay Area new music scene, Ms. Brouk blazed her own trail well outside of the musical establishment to create uncompromising electronic and acoustic work of sleek beauty and primal power. Describing herself as less a composer than a channel, she took her cues from the frequencies of the natural world and the talents of collaborators like Maggi Payne and Bill Maraldo. Hearing Music collects for the first time the deepest cuts from her beguiling and rare cassette releases and her archive of previously unreleased recordings.