One the biggest trends in publishing in the U.S. is the surging digital audio market, where the format has been posting hefty double-digit growth for years, and making up an increasing share of publishers’ digital sales. At the Frankfurt Book Fair’s inaugural Audiobook Conference on Wednesday, experts told attendees that the audio boom is indeed a global trend, with more growth to come.

Henrik Lindvall, head of rights team management for Swedish-based Storytel, a major new player in the audio market, said the format is hugely popular in Scandinavia, growing fast in many European countries and the U.K., and is now poised for major growth in emerging markets, like India, where Storytel is planning a major push. “The opportunity is India is huge,” Lindvall said, noting a massive smartphone market, and a large middle class that is used to the subscription model, thanks to Netflix and Amazon Prime, which have large customer bases there.

John Ruhrmann, managing director co-founder of Bookwire, also offered his view not only on the audiobook’s current growth, and more importantly, its still untapped potential. Ruhrmann urged publishers to address “all relevant business models” without always thinking of turnover. “Turnover is not a strategy,” Ruhrmann said. “No fear, try more, learn by testing and doing.”

A former music industry employee, Ruhrmann suggested that trends in music are worth watching for audio publishers, especially when it comes to streaming services. “Streaming is now making up a real big portion of the revenues of the music industry,” he said. “I know it is difficult to say that the music industry might be same as the book industry, but it is a trend, and we should watch this trend and know how to deal with it.”

In fact, in his opening keynote at the Markets, HarperCollins UK CEO Charlie Redmayne acknowledged that audio consumption for publishers does in fact “look more like music listening than book reading.” And he pointed to audio in the U.K. “growing double digits year-on-year with no sign of slowing down.” Better still, he added, audio shows no signs of “eating into print or e-book share.”

After years of massive digital change being predicted for publishers, Rurhmann acknowledged that some publishers may be skeptical of such claims these days. But when it comes to audio, with new platforms, models, and ever powerful technology, a digital revolution for publishers has in fact materialized. “I can tell you,” Ruhrmann said, “it’s here.”

Amanda D’Acierno president and publisher, of Penguin Random House Audio in the U.S., offered insight into the publisher’s strong growth in audio, telling publishers that since 2014, the first year of Penguin Random House, post-merger, its audio output has more than doubled, from 652 to more than 1,300 titles.

“What’s really changed is that agents and authors want their audiobooks produced. So when they are selling rights to publishers, they expect the audiobook will be produced simultaneously with the book,” D’Acierno said. The growth in digital audio has also allowed the publisher to expand into new categories, she said, such as short stories, which previously did not really work in audio.

Finally, D’Acierno also spoke of how the popularity of audio has changed the way authors approach their work—and she cited a book that is certain to be huge bestseller not only in print, but in audio: Michelle Obama’s forthcoming memoir Becoming. In the past, major celebrity authors and politicians would only go in the studio to do abridged audio editions of their books. Not any more.

“Michelle Obama spent six and a half long days in the studio, recording morning until evening,” D’Acierno said. “There is no other person that could read this story, and consumers want that experience.”