Music is also present in the film, in this case it is a song called "Blue Moon". As Jasmine repeatedly explains, this song was playing when she and Hal met. This song reminds her of her high-society priviliged life that she no longer has. "Blue Moon" is the blue piano that, as Williams wrote in the play, it expresses “the spirit of the life which goes on here.”
Every time she feels nostalgic about her past she imagines the song playing in her head and loses her grip on reality. She neglects the reality in which her actions led her to and recreates a fantastic life through her memories of when she was a socialite.
Similarities in music in the play and the film
In "A Streetcar named Desire" the Varsouviana Polka and “It’s Only a Paper Moon,” trigger memories of Blanche's young husband’s suicide and symbolize her descent into fantasy and madness. Blanche can’t escape feeling to blame for her husband’s suicide because she confronted his sexuality.
This is the same in "Blue Jasmine", when Jasmine reveals her husband's crimes to the police, leading to Hal’s arrest and later, his suicide. Despite everyone believing that she knew nothing of Hal's financial indiscretions, she ends up revealing that she has known everything all along.
Both Jasmine and Blanche prefer to retreat back into a fantasy world of feigned ignorance and fragility than to confront their true reality.