‘I don’t know if it is theatre,” Enda Walsh says of his new show. In his upcoming piece, Rooms, recorded voices bounce off the walls of five different spaces including a child’s bedroom, cluttered with toys, and a cheap, chintzy hotel room with floor-to-ceiling florals. Through each floats a disembodied voice. It is, in a way, theatre without actors; a play, but with no performers present. “I wouldn’t classify it as theatre,” the playwright demurs, “but I don’t know exactly what it is.”

It’s 50 years since Peter Brook laid down a definition that, for a long time, served theatre well. “I can take any empty space and call it a bare stage,” he wrote. “A man walks across this empty space while someone else is watching him, and this is all that is needed for an act of theatre to be engaged.” Somebody watching someone else stepping into a space.

Though Rooms falls short of this description, it still feels like theatre. “Why isn’t it a radio play?” Walsh wonders aloud. But Rooms is more than a mere recording. The space is integral – “all the indicators are there in the design” – so our presence is required. Each room is theatrical. We scour the spaces for clues. What does this travelling salesman think about, lying on this B&B bed? Why has this grown woman fled this family home? The game is to figure out how the two might sit together: speaker and space. “It’s like that awful, addictive television programme Through the Keyhole,” Walsh jokes. Who would live in a house like this?

‘I don’t know exactly what it is’ … Enda Walsh’s Rooms. Photograph: Andrew Downes/Urbancow/Xposure for Galway International Arts festival

A year after Brook’s book The Empty Space was published, Samuel Beckett rendered its opening statement defunct. He wrote a play, Breath, without any people. Lights up on a stage piled high with mess – one inhale, one exhale – lights out. It lasts scarcely 30 seconds, but it is, surely, a play, even without performers. When Kenneth Tynan added a chorus of naked bodies, Beckett threatened litigation.

All sorts of artists have challenged Brook’s mantra since. In London in 2008, Heiner Goebbels staged Stifter’s Dinge, a conceptual composition for five pianos – featuring no pianists.

Theatre is often framed in terms of presence – the liveness of a performance – so its omission can feel glaringly apparent. So much so that the absence itself can have a presence. In Rooms, that is Walsh’s primary theme. His characters are “disparate people on the edge of everything, wondering whether to stop or carry on. They feel the complete emptiness of everything and talk into the nothingness.”

Traces of someone just gone … The Drowned Man by Punchdrunk. Photograph: Tristram Kenton/The Guardian

In Punchdrunk’s shows, absence often makes its presence felt. You step into a space to find traces of someone or something just gone: a table knocked over or a smoking cigarette butt. That absence can transform into action. The company’s very first show invited audiences to an apparently abandoned theatre and waited for them to summon enough pluck to pick up the telephone ringing on stage.

At the Royal Court, Dismantle This Room goes further still. Created by Milli Bhatia, Ingrid Marvin and Nina Segal, it’s an escape room constructed on the main stage, themed around the power structures of British theatre. Over an evening, 15 people have to discover a way out by disentangling the industrial hierarchies around the art form. “We wanted to put audiences right at the centre,” explains writer and dramaturg Segal. “What is the most agency we can possibly give them?”

Participants in Dismantle This Room. Photograph: Hassan Joof

There may be no actors but Marvin says that “an escape room has everything a good show has: strong narratives, plot twists, a sense of engagement”. Arguably, in this sort of participatory theatre, audiences double as performers and spectators. “Artistically and politically, we really like the idea of allowing an audience to take their place on the Royal Court stage,” says Segal.

The challenge is imparting information and, as in Rooms, audiences end up scouring the space for clues. Discarded emails deliver plot twists. Unmanned walkie-talkies pipe up. The four co-creators sit, out of sight, steering and responding to audiences’ choices and “live-making” the show night after night. It’s as if the space itself starts to perform and that, perhaps, is the rejoinder to Brook – that no space is ever empty, even without actors.