What is the importance of melody and music in Trifles by Susan Glaspell?

By this question I am assuming you mean, "Discuss the role of music in the play." Music or melody is significant in Triflesas a symbol for Minnie Wright, the woman suspected of murdering her husband. In the days before her marriage, Minnie used to sing in the choir and had a lovely singing voice. However, after her marriage, she became isolated, lived in near poverty, and was more or less imprisoned in the dreary...

By this question I am assuming you mean, "Discuss the role of music in the play." Music or melody is significant in Trifles as a symbol for Minnie Wright, the woman suspected of murdering her husband. In the days before her marriage, Minnie used to sing in the choir and had a lovely singing voice. However, after her marriage, she became isolated, lived in near poverty, and was more or less imprisoned in the dreary farmhouse by the gruff and insensitive Mr. Wright.

Mrs. Hale and Mrs. Peters find a bird cage, and Mrs. Hale recalls that a man was going through the area selling canaries, a type of song bird. They suppose Minnie bought a canary and that must have cheered her in her loneliness. Soon they find the dead body of the canary, its neck twisted. As Mrs. Hale says, Minnie "was kind of like a bird herself." Then to draw a comparison between Mr. Wright's killing the bird and his abuse of his wife, she says, "She used to sing. He killed that, too." Mrs. Hale imagines how still it would have seemed in the farmhouse once the bird's music had been silenced. 

In the play the way that Mr. Wright "killed" the music in both Minnie and the bird present a motive for Mrs. Wright's action but also enough of a justification that the two women decide to not share the evidence they have found.