If we had to describe the sound of "Remember" in two words, those two words would be "commanding" and "consoling." We'll just call them the two C's. And it makes sense that we need two words to describe the sound of this poem because, well, it's a sonnet, and sonnets are often divided into two parts (an octave and sestet), which you can read more about over at "Form and Meter."
So, without further ado, let's dig into this poem's sound. The poem's title is a command—"Remember." That same command is repeated three more times in the poem, at lines 1, 5, 7. In addition to this repeated imperative, there's also that "do not grieve" in line 10. Now even though this poem is definitely marked by a commanding tone, it's not the same tone your mom would use when yelling at you to clean up your room. It's a gentler kind of commanding. Note, for example, that the speaker's orders are often flanked by tender recollections (all that hand-holding business, for example).
Notice, too, that you get some alliteration in the first section to soften the commanding blow. Check out all the H words in "When you can no more hold me by the hand, / Nor I half turn to go yet turning stay" (3-4). Those soft, breathy Hs make the line seem less sharp and demanding, more desperate in a way with the panting desire of the speaker's plea.
The commands in the first section are also flanked by various consoling remarks. This brings us to our second sonic quality. When the speaker tells her beloved not to grieve, technically she is commanding or ordering him, but she's also speaking like a comforting friend, or lover, or parent, or what have you. It's "Please do not grieve sweetheart," not "HEY! I SAID DON'T GRIEVE, BUSTER!" This consoling tone can be heard in the poem's alliterations here, too, with the B and F words (no, not those F words) in "Better by far you should forget and smile" (13). The combinations create a sonic symmetry in the line that puts the ear at rest, soothing us as the speaker soothes her lover.
Besides these two major tones, we need to address the fact that there's a lot of repetition in the sounds of this poem. If you've read our "Form and Meter" section, you know that this poem's rhyme scheme is cyclical. That, combined with the alliterative repetitions, represents sound that "comes back," reinforcing one of the poem's major themes. "Remember" is about how people are dead can come back to life, or be kept alive, via the memory. The way in which these sounds keep returning makes the same claim at the level of sound. Pretty cool, if we do say so ourselves.