PROVIDENCE, R.I. — Sarah Bertness slipped into her seat at a recent staging of a musical and, when the lights dimmed, started doing something that’s long been taboo inside theaters: typing away at her iPhone.

The 26-year-old freelance writer wasn’t being rude. She had a spot in the “tweet seat” section at the Providence Performing Arts Center.

The downtown theater is now setting aside a small number of seats in the back for those who promise to live-tweet from the performance using a special hash tag. They might offer impressions of the set, music or costumes, lines of dialogue that resonate or anything else that strikes them.

A growing number of theaters, including some on Broadway, have been experimenting with tweet seats and other real-time uses of social media as they try to figure out the relationship between the stage and the smartphone.

Some insist the theater should remain a sacred, technology-free place and that allowing the use of phones during a show only serves as a potential distraction for other patrons. But others say theaters can’t afford not to engage the digital generation, and that the way performances once were enjoyed in a vacuum doesn’t hold up.