Prior to line fifteen, in Adrienne Rich's poem "Living in Sin," a woman is depicted as thinking about how the studio she shares with her lover "would keep itself." The woman seems disgusted at the fact that the studio is dirty. She seems to believe that the state of the studio is the fault of her lover. Therefore, one can almost see the woman scowling at her lover as he plays messes around. This leads the reader to believe that the woman is less than happy with her lover's lack of concern for the state of the studio.
Meanwhile, her lover is depicted as playing the piano, becoming disgusted at the piano's tune, and leaves for cigarettes. When the lover leaves, the woman begins to clean the studio. In the end, she "was back in love again" with her lover.
Therefore, the two events which take place simultaneously during the poem is the woman showing her detest of the studio's state and the lover playing the piano, getting disgusted at the piano being out of tune, and leaving the studio.
The action of the woman cleaning takes place after the lover leaves and cannot be tired to the simultaneous events in question.