Listening to the voices of Sylvia Plath and Anne Sexton is a powerful acoustic experience. When I began the research for my new book, Three-Martini Afternoons at the Ritz: The Rebellion of Sylvia Plath & Anne Sexton, I spent many months in archives reading letters, looking at poetry manuscripts, and handling personal possessions such as typewriters, address books, even hair. But time spent in the audio rooms gave a unique insight into the physicality of these two women.

Imagine sitting alone in a booth, wearing noise-canceling headphones, and turning the volume up loud to hear a tipsy Anne Sexton sing Christmas carols with her neighbor, or Plath chuckle her way through describing eccentric Englishisms she’d noticed since moving to England with her husband, fellow poet Ted Hughes.

I could hear their breathing, their moving around, the creaking of their furniture. In the case of Sexton, the ice in her drink clinked away as she took long swigs, and her dog was barking somewhere in the distance. Plath was so witty I could hear her interviewer stifling his snorts of laughter.

Both women had deep voices, with a rich timbre. Plath’s was wry-sounding, with a curious mix of New England and Yorkshire accents. Sexton’s was a lazy drawl.

When they read their work, it was a true performance. Hearing which words and phrases they emphasized led me to a new awareness of some of their poems. I had always understood the end of Plath’s “Daddy” to be defiant and angry. But her reading evoked less convincing defiance and more weary dismissiveness. Meanwhile, Sexton’s swirling performance of “Music Swims Back to Me,” with a band she had formed called Her Kind, was jubilant, ecstatic, and nowhere near as sad as I had previously interpreted it.

My book focuses on Plath and Sexton’s social rebellion, and all the ways in which they flouted the norms and expectations of their cultural moment, and it was thrilling to learn that their audio presence was as powerful as their textual presence. Both had a commanding quality. I imagine it would have been impossible to ignore them when they entered a room.

Sexton runs the gamut of emotions in her recordings: cranky (at being interrupted), bemused (on topics of sex and death), upset (at the loss of a beloved family member), and scolding (at an incompetent interviewer). Plath’s are much steadier—she is earnest, a little caustic, sardonic, and droll. Sometimes her barely suppressed anger unnerved me.

But if one thing surprised me more than any other about listening to Sylvia Plath and Anne Sexton, it was how their voices humanized them. They were no longer these dizzyingly untouchable writers. They were living, breathing women. Extraordinary women, but alive and real.

Gail Crowther is the author of The Haunted Reader and Sylvia Plath. Her latest book, Three-Martini Afternoons at the Ritz: The Rebellion of Sylvia Plath & Anne Sexton, is out now from Gallery