At first, "Auguries" can sound kind of like a little kid reciting some sort of proverb in an old-timey schoolroom. They have an "Early to bed, early to rise / Makes a man healthy, wealthy, and wise" feel to them—though Blake was way different as a person from pearl-of-wisdom-dropping folks like Ben Franklin. "A truth that's told with bad intent / Beats all the lies you can invent" (53-54) is a decent example of this kind of Blakean wisdom.
What initially sounds like a schoolish, proverbial vibe, though, can start to feel more like a magical incantation, going along to a steady, insistent drum beat. It begins to seem more ancient and weird—something they might recite in between songs at a Spinal Tap concert. A good example comes close to the end of the poem:
Every night and every morn Some to misery are born, Every morn and every night Some are born to sweet delight. Some are born to sweet delight Some are born to endless night. (120-124)
That beat is as heavy as Zeppelin. As for other sonic effects, Blake's occasional slant rhymes can create an off-kilter, life-out-of-balance feel to our modern ear. In all likelihood, these were not originally slant rhymes for the accent of his time and place. All the same, we encounter several nearly-rhyming couplets like "The Babe that weeps the Road beneath / Writes Revenge in realms of Death." (73-74). And he also throws in the occasional hard-charging alliteration: "The Bleat, the Bark, Bellow, and Roar / Are Waves that Beat on Heaven's Shore" (71-72).
It's probably fair to say, though, that the poem gets its energy more from rhythm than from doing unusual things with vowel sounds and so on—Blake doesn't really repeat vowel sounds too frequently. He shoots for variety. But the driving beat (check out "Form and Meter" for a breakdown) turns the poem from being a quaint schoolyard chant into something way more primal—something ancient priests would recite around a stone altar in a forest.