After they discuss the plan , Marcellina and the Countess leave , and Susanna deliberately sings a love song to her beloved near to where Figaro is so that he can hear it . After they discuss the plan , Marcellina and the Countess leave , and Susanna teases Figaro by singing a love song to her beloved within Figaro 's hearing ( aria : Deh , vieni , non tardar -- `` Oh come , do n't delay '' ) .