Donald J. Trump was about 30 minutes into a town hall Monday night in suburban Philadelphia when a medical emergency in the crowd brought the questions and answers to a halt. Moments later, he tried to get back on track, when another medical incident seemed to derail things, this time for good.

And so Mr. Trump, a political candidate known for improvisational departures, made a detour. Rather than try to restart the political program, he seemed to decide in the moment that it would be more enjoyable for all concerned — and, it appeared, for himself — to just listen to music instead.

Mr. Trump had his staff fire up his campaign playlist, standing on the stage for about half an hour and swaying to songs as his crowd slowly dwindled.

He bobbed his head through the Village People’s “Y.M.C.A.,” his usual closing song. He swayed soberly to Rufus Wainwright’s version of “Hallelujah,” watched a Sinead O’Connor video, rocked along to Elvis, watched the crowd during “Rich Men North of Richmond” and then, finally, left the stage to shake hands on his way out during one last song.

The impromptu D.J. session was a strange conclusion to a political event that had started on familiar turf. Aided by Gov. Kristi Noem of South Dakota, Mr. Trump answered questions in front of hundreds of people at the Greater Philadelphia Expo Center in Oaks, Pa., about 18 miles northwest of Philadelphia.

The inquiries from friendly audience members allowed Mr. Trump to rattle off a series of talking points about the economy and immigration and attacks against Vice President Kamala Harris. But the event’s tone shifted about 30 minutes in, when two people in the crowd needed medical attention after apparently passing out.

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