Analysis of Xvii

My poet, thou canst touch on all the notes
God set between his After and Before,
And strike up and strike off the general roar
Of the rushing worlds a melody that floats
In a serene air purely. Antidotes
Of medicated music, answering for
Mankind's forlornest uses, thou canst pour
From thence into their ears. God's will devotes
Thine to such ends, and mine to wait on thine.
How, Dearest, wilt thou have me for most use ?
A hope, to sing by gladly ? or a fine
Sad memory, with thy songs to interfuse ?
A shade, in which to sing--of palm or pine ?
A grave, on which to rest from singing ? Choose.