Asmiʿī is a feminine singular imperative from form IV, with -nā its first-person plural object: “let us hear.” Inbarat is third-person feminine singular past, referring to the singer. Idhā naḥnu qulnā introduces the recurring occasion of a request and its response.
Lam tushaddad uses the negative particle lam with a jussive imperfect, conveying that the performance was not forced or made harsh. The grammar links the request, reaction, and quality of the voice into one continuous scene.