Hilary Hahn’s solo recital at the Folly Theater on Friday, October 13, administered spiritual balm in a fraught moment. The violinist offered 90 minutes of ethereal restoration for members of the near-capacity audience of about 950 rattled by current events. The room’s excellent acoustics allowed Hahn’s elevated reading of four timeless works by Johann Sebastian Bach to sanctify the back row seat I purchased for $20. The event was less a concert than a consecrated prayer.