"Impish musics"- mischievous musicians; "crumble the ecstatic loaf/ before a swooning flock of doves"- doves can mean "birds," or, women, or the audience in general, flocking to the music. The ecstatic loaf is the music, being crumbled and feasts upon by the audience of doves. They are joyous, entertained, and fulfilled, unlike the speaker, who is alone and lamenting her late husband.