Such is the power of the Edinburgh Intl. Festival and Fringe that the population of the Scottish capital doubles during August. The city pulses with cultural tourists, and the relationship between actors and audiences is at its most intense. This summer, that relationship emerged as a theme in itself.

In some cases this was explicit. In “The Event,” given simultaneous productions in Edinburgh and in Gotham’s Intl. Fringe Festival, playwright John Clancy picked apart the act of staging a play in forensic, postmodern detail. Thesp David Calvitto (Matt Oberg plays the part in New York) spent an hour telling us about being an actor in the play we were watching, but before the metatheatrical games were through, he turned the tables to accuse us of treating real life as a similar kind of spectator sport.

Nobody questioned the role of the audience more unsettlingly than Belgian company Ontroerend Goed. In “Internal,” five audience members lined up in front of five actors and found themselves paired off for a one-on-one speed-dating session. After 15 minutes of animated conversation — or embarrassing silence, depending how well each couple hit it off — the 10 people reconvened for some group therapy.

If you clicked, you could find yourself in a passionate embrace with a pretty actor. If the sparks failed to fly, you sat there squirming. Either way, you left in a state of emotional turbulence, quite unable to determine where reality had blended with artifice.

One of the most talked about shows on the Fringe was “Trilogy” by the young dancer and theatermaker Nic Green. In an effort to re-engage with feminist ideas — most notably those expressed in “Town Bloody Hall,” a landmark debate involving Germaine Greer and Norman Mailer in Gotham, 1971 — Green invited a group of local women to dance naked with her.

By the end of the performance, many women in the audience accepted her invitation to remove their clothes for a rousing (but not arousing) chorus of “Jerusalem,” a startling example of women reclaiming their bodies from the tyranny of the male gaze.

It sounds shocking, but Green made it feel natural, as did playwright David Greig when, during a rehearsed reading of “Brewers Fayre,” he asked the early-morning audience to play the part of the chorus. The relevant lines were projected onto a screen and the audience performed with surprising gusto. It was a clever way of exploiting the unspoken pact between spectator and performer, and made this funny new play about adultery all the more engaging.

Edinburgh audiences have grown used to site-specific theater and thought nothing of dressing in white kimonos for David Leddy’s intimate “White Tea,” about a woman reconnecting with her estranged Japanese mother. Likewise, they freely accepted a drink from the bar for Grid Iron theater’s “Barflies,” based on the stories of Charles Bukowski and performed in a real-life watering hole.

This also meant auds were primed for Mark Watson’s “The Hotel,” possibly the world’s first example of site-specific comedy, in which the audience played guests in a “Fawlty Towers”-style inn run by a neurotic staff with no concept of customer relations or health and safety regulations.

You expect such experiments on the Fringe, but similar realignments were made in the Intl. Festival as well. In Silviu Purcarete’s majestic “Faust,” once Ilie Gheorghe’s scholar and Ofelia Popii’s sexually ambiguous Mephistopheles had made their pact, the back wall disappeared from behind them revealing a carnival-like vision of hell taking place in a massive hangar-like space. Ushered out of their seats, the audience joined an increasingly skeptical Faust among the theatrical fireworks and flames.

More subtly, Brian Friel toyed with our suspension of disbelief in “The Yalta Game” — one of three of his plays staged consummately by Dublin’s Gate Theater — in which he drew a parallel between the escapist fantasy of a holiday romance and our willingness to escape into the fictional world of the stage.

The Edinburgh Fringe wrapped Aug. 31, while the Intl. Festival closed Sept. 6.