India, Sept. 22 -- On a night when rain poured in sheets, my husband and I braved Delhi's gridlock and the notorious parking hunt to reach a stranger's home. We had, in fact, paid to be there. Inside, about 40 people sat cross-legged on rugs as a young sitarist tuned her instrument, joined by a tabla player. No velvet curtains, no stage lights, no professional sound system. Yet, as the music began, a stranger's living room instantly fell like home.

Baithaks, intimate and hyper-local ticketed concerts held in homes, are quietly reshaping Delhi's cultural landscape. For many millennials, they are both a throwback to childhood memories of baithaks at grandparents' homes and a new experiment in intimacy in a city crowded with strangers.

In ...