The Gladiator star invited members of the cast and crew over to his pad in France for weekly get-togethers and he made sure to supply plenty of alcohol so actors including Hugh Jackman, Anne Hathaway and Amanda Seyfried would be comfortable enough to gather around the piano and take part in a little jovial singing.
And Hathaway, who portrays tragic prostitute Fantine, admits the drunken parties became something to look forward to at the end of each trying week.
The actress tells Vogue magazine, ""Considering how miserable I was on set every day, some of my happiest memories are from those sing-alongs.
""After that, once we got in front of the cameras, it didn't feel weird bursting into song around each other.""
Sing-along highlights included Hathaway's rendition of The Man That Got Away, Seyfried's version of Sister Rosetta Goes Before Us by Robert Plant and Alison Krauss, and a group cover of Adele's hit track Someone Like You.