Not only does he keep to one idea in it, but he finishes the poem like a cameo.

Here is an instance wherein he outdoes the elaboration of a Norman trouvere; for not merely does each line in each stanza end with the same sound as the corresponding line in every other stanza, but it ends with the very same word.

I shall hardly care to defend this if my reader chooses to call it a whim; but I do say that a large degree of the peculiar musical effect of the poem--subservient to the thought, keeping it dimly chiming in the head until it breaks out clear and triumphant like a silver bell in the last--is owing to this use of the same column of words at the line-ends of every stanza.

Let him who doubts it, read the poem aloud.
AARON.
Holiness on the head; Light and perfections on the breast; Harmonious bells below, raising the dead, To lead them unto life and rest-- Thus are true Aarons drest.
Profaneness in my head; Defects and darkness in my breast; A noise of passions ringing me for dead Unto a place where is no rest-- Poor priest, thus am I drest! Only another head I have, another heart and breast, Another music, making live, not dead, Without whom I could have no rest-- In him I am well drest.
Christ is my only head, My alone only heart and breast, My only music, striking me even dead, That to the old man I may rest, And be in him new drest.
So, holy in my head, Perfect and light in my dear breast, My doctrine turned by Christ, who is not dead, But lives in me while I do rest-- Come, people: Aaron's drest.
Note the flow and the ebb of the lines of each stanza--from six to eight to ten syllables, and back through eight to six, the number of stanzas corresponding to the number of lines in each; only the poem itself begins with the ebb, and ends with a full spring-flow of energy.

Note also the perfect antithesis in their parts between the first and second stanzas, and how the last line of the poem clenches the whole in revealing its idea--that for the sake of which it was written.