Part One, Envoi Summary

Lines 218-224

Envoi (1919)

Go, dumb-born book,
Tell her that sang me once that song of Lawes;
Hadst thou but song
As thou hast subjects known,
Then were there cause in thee that should condone
Even my faults that heavy upon me lie
And build her glories their longevity.

• Well first thing's first: the French word "envoi" means an "envoy" or a sort of afterthought to a poem or book of poetry. So Pound is signaling to us that he's going to wrap up his thinking about the modern world, at least when it comes to Part One of "Mauberley." 
• So now, Pound is saying "Go, dumb-born book." Dumb here probably refers to being unable to speak, but it could also mean stupid. So Pound might not be totally optimistic about what this poem is going to achieve. 
• Next, Pound is asking his poem to deliver a message to a woman that once sang a song to him by an English composer named Henry Lawes. Pound wants this woman to know that he wishes she had "song/ As thou hast subjects known." In other words, Pound wishes the woman had known as much about beautiful singing as she'd know about "subjects," which here might refer to meaningless trivia. In this case, Pound might be mocking modern educated women, who might know a lot about many subjects, but have no clue how to be beautiful. And yes, that's kind of sexist. 
• In the last three lines, Pound says that if the woman truly knew beauty, she'd be able to "condone" or put a stamp of approval on all of Pound's faults that lie "heavy upon him." Further, the woman would be able to build her own "glories" in their longevity. In other words, the woman would be like a woman from Greek myth, and her beauty and "glories" would be celebrated long after she'd grown old and wrinkled.

Lines 225-233

Tell her that sheds
Such treasure in the air,
Recking naught else but that her graces give
Life to the moment,
I would bid them live
As roses might, in magic amber laid,
Red overwrought with orange and all made
One substance and one colour
Braving time.

• Next, Pound describes the woman as shedding "treasure in the air." Just think about that for a second. It's kind of like the way a beautiful song works, right? It exists totally in the moment, and disappears when people's breath comes out of their bodies into the air. 
• On line 227, the word "Recking" means having concern for something. So Pound says that the female singer doesn't care about anything other than making her song beautiful so it can give life "to the moment" before it disappears into the air. In this sense, Pound is willing to admit the song is beautiful, but he wishes it was something that could last longer. 
• That's why in lines 229-233, Pound says he wishes that he could take the woman's singing and seal it in amber to keep it preserved forever, the way people sometimes do with roses. For those of you who haven't seen Jurassic Park, amber or hardened tree sap is really good at preserving stuff. The symbol of the rose sealed in amber helps show Pound's desire for art to create something beautiful that isn't just for modern audiences, but that can stay beautiful for centuries, "Braving time" like Greek myth.

Lines 234-243

Tell her that goes
With song upon her lips
But sings not out the song, nor knows
The maker of it, some other mouth,
May be as fair as hers,
Might, in new ages, gain her worshippers,
When our two dusts with Waller's shall be laid,
Siftings on siftings in oblivion,
Till change hath broken down
All things save Beauty alone.

• Pound is still telling his poem what he wants the symbolic singing woman to know. He says that he wants the woman to know that even though she doesn't know the person who wrote the song she's singing, it's the beauty of the song that matters. You can basically see the meaning of this stanza if you jump ahead to the last two lines right away, which talk about time and change eroding or breaking down everything except Beauty. The fact that Beauty is spelled with a capital B shows that Pound thinks it's something bigger than any one person, almost like a god.
• In any case, the thing Pound wants the singing woman to know is that the beautiful song is what matters, and that's what she should be focusing on. Any woman who sings the song will eventually get old and die. And in the future, "some other mouth" or some other singer might get new people to enjoy the song. 
• Pound mentions how both the singer and himself will eventually die and be laid with the dust of someone named Waller.
• Waller refers to English poet Edmund Waller, whose poem "Go, Lovely Rose" is what Pound is basically copying for his own purposes in this section of "Mauberley." 
• But yeah, for Pound it's beauty that matters. We're all going to die someday, but the beauty of great art is like a rose sealed in amber, preserved forever.