Many film critics agree that the success of "Frozen" can be attributed to two things—the fresh plot of the film, which deviates from the traditional formula of Disney princess movies, and the film's music. The animated film's songs were written by husband and wife songwriting team Robert Lopez and Kristen Anderson-Lopez, and the couple won an Oscar for Best Original Song for "Let it Go."

After the film was released in November 2013, many fans took to YouTube to record their own versions of the song, and children around the world continue to cite the song as one of their favorite Disney movie songs of all time.

Lopez recently gave an update about a song that he and Anderson-Lopez have been working on. It was previously reported that Kristen Bell, Idina Menzel, Josh Gad, and Jonathan Groff are expected to return to reprise their roles as Princess Anna, Queen Elsa, Olaf, and Kristoff, and Lopez and his wife will also be returning to write new songs for the upcoming film.

Back in September, the songwriter took to Twitter and wrote, "It's awe inspiring to study the @starwars saga soundtracks as we consider adding to the music of #Frozen."

Apart from the sequel, the couple is also working on music for "Frozen the Musical". On Thursday, Nov. 12, Lopez took to the micro blogging site and wrote, "Finally wrote a duet for Anna and Kristoff! Apologies to Groffsauce for the lateness."

Anderson-Lopez also tweeted on the same date in response to her husband's post and wrote, "Why didn't we think of this before? It was so fun to write!"

For now, it is unclear whether the new duet was written for the film or the musical. Fans took to Twitter and asked the couple to clarify where the duet will be featured, but the songwriting duo has yet to reply to their tweets. In the first film, Anna and Kristoff never sang together, and Kristoff only sang a short song to his reindeer, Sven.

Disney has yet to announce a premiere date for "Frozen 2."