Music is an important symbol of celebration and happiness
1. Music is central to the Christmas celebrations at Fezziwig's party and at Fred's house, and Dickens also mentions the singing of Tiny Tim, the miners and the lighthouse men
2. There's a strong contrast between the joy and happiness of Fred's "musical family" and the lonely, miserable Scrooge, whose life is without music (this is emphasised when Scrooge scares away the carol singer in Chapter One)
3. Music is also shown to have a powerful emotional effect. When Scrooge hears some music performed by his niece (Fred's wife), he wonders whether if he'd be able to listen to it more, "he might have cultivated the kindness of life for his own happiness with his own hands". Dickens is arguing that music is so powerful in creating creating happiness that it could've transformed Scrooge's life