"Six By Sondheim" is a new HBO documentary that takes a look at the life and art of musical theatre legend Stephen Sondheim through six of his iconic songs. Directed by Tony winner James Lapine, the film contains archival footage as well as new musical segments directed by Todd Haynes, Autumn de Wilde and Lapine. In this special peek at the new performance of Merrily We Roll Along's "Opening Doors," (courtesy of HBO) Darren Criss, Jeremy Jordan, America Ferrera and Laura Osnes reflect on their experiences performing in the documentary. "Six By Sondheim" debuts Dec. 9 on HBO.