The lovely-voiced pop-classical crossover phenom Josh Groban, the star of Broadway’s Natasha, Pierre & the Great Comet of 1812 and your aunt’s favorite singer in the world, treats fans to his first-ever holiday concert, part of a fall virtual-performance series to promote his brand-new album, Harmony. Expect “O Holy Night” (already a deservedly loved staple of Groban’s repertoire) and other seasonal favorites. Tickets start at $30.