When I am dead, my dearest,
Sing no sad songs for me;
Plant thou no roses at my head,
Nor shady cypress tree:
Be the green grass above me
The narrator rejects the showy, sentimental funerals that became popular during the Victorian era. The  alliterative  ’s’s, monosyllables and elongated vowels slow the pace of this line, as if mimicking the sad singing referred to.
Song When I am dead my dearest