The event is the culmination of six weeks of fundraising for Broadway Cares/Equity Fights AIDS.
This year's WhatsOnStage Awards nominees are led by Miss Saigon, Memphis, and Urinetown.
John R. Waters sings the hits of the late Beatle at the Union Square Theatre.
The Broadway vet won a 2013 WhatsOnStage Award for his London performance as the sweet-voiced Mormon missionary.
Beasts of the Southern Wild cowriter Lucy Alibar is among the artists developing projects.
The Classic Stage Company production of Ivan Turgenev's A Month in the Country will be directed by Erica Schmidt.
The play's original Atlantic Theater Company cast members Stephen McKinley Henderson and Victor Almanzar will also star.
Broadway favorites Kelli O'Hara, Christian Borle, and Taylor Louderman can also be seen in the live performance tonight.
Both performers will step into their roles on January 7.