The video has been viewed nearly 26,000 times since it was posted on YouTube Monday.
Season 3 of the show recently wrapped in the United States.
The musical video is being billed as the eagerly awaited first episode for the upcoming fourth season.
"The guys and I were all 'Downton' fans and while spitballing ideas, we said, 'Well, "Buffy" & "Grey's" did a musical episode,' and we thought of ['Downton' creator] Julian Fellowes in a room with [fellow writer-producers] Shonda Rhimes and Joss Whedon trying to plan out the inevitable 'Downton Abbey' musical episode in Season 4," producer Kevin Duda told EW.com.
Colin Andrew Mochrie, a comedian best known for his work on "Whose Line Is It Anyway?," plays Fellowes, who explains in the video he wanted to create a "Downton" musical in New York as a treat for American fans upset because the show always airs in the United Kingdom before it hits U.S. television screens.