The account, The AIDS Memorial, is an evolving testament, told in photographs, videos and user stories, to lives lost to a devastating and, it can occasionally seem, forgotten epidemic. To date, Mr. Armstrong has posted more than 11,000 of these tales, and if you are aware of them at all, that may owe to one woman: Madonna. The 65-year-old singer was early among the 269,000 followers of The AIDS Memorial. And, if it did not inspire her outright, the Instagram account served as the basis for a showstopping element of her current “Celebration” tour, which comes to Barclays Center in mid-December. By extension, Madonna’s choice to deploy the montage early in each “Celebration” performance as a backdrop for a rendition of the 1986 song “Live to Tell” is as politically trenchant as it is deeply personal.

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Persons: Stuart Armstrong, Armstrong, Sarah Schulman —, —, Martin Burgoyne Organizations: Barclays Center, World Health Organization, The Locations: Edinburgh, York, British