"Booksmart"'s Beanie Feldstein, former "Glee" actor Blake Jenner and Broadway star Ben Platt have signed on for the long haul, with Linklater, who shot "Boyhood" over 12 years, confirming he will film segments every year over the next 20.
"I first saw, and fell in love with Merrily in the '80's and I can't think of a better place to spend the next 20 years than in the world of a Sondheim musical," the moviemaker tells The Hollywood Reporter. "I don't enter this multi-year experience lightly, but it seems the best, perhaps the only way, to do this story justice on film."
The musical is told in reverse, starting in 1976 and reaching the point where the characters originally met, 20 years earlier.
Platt will star as a Broadway composer, who relocates from New York to Los Angeles, while Feldstein will play his theatre critic best friend.
The project marks a reunion for Jenner and Linklater - the actor starred in the director's 2016 college film "Everybody Wants Some".