The language of "Elegy Written in a Country Churchyard" is musical and melodious—thanks in large part to the poem's assonance, some striking examples of which we've highlighted in this guide. The poem's carefully doled out assonance simply makes it pleasurable and easy to read, and it also helps makes the poem's imagery more vivid.
For instance, the speaker repeats the long /o/ sound in the first two lines:
The curfew tolls the knell of parting day,
The lowing herd wind slowly o'er the lea,
The assonance here evokes the poem's somber setting. Those round, open /o/ sounds suggest the slow "toll[ing]" bells or the deep "lowing" noises made by a nearby herd of animals.
The speaker often sustains the same assonant sound across many lines as well, making the poem feel cohesive and lyrical. Take lines 13-17, for example, in which the relentless /ee/ sound makes the poem feel carefully crafted:
Beneath those rugged elms, that yew-tree's shade,
Where heaves the turf in many a mould'ring heap,
Each in his narrow cell for ever laid,
The rude forefathers of the hamlet sleep.
The breezy call of incense-breathing Morn,
This repeated sound also links each image at hand—the trees, the heaps of dirt, the corpses, the morning—into one coherent environment. As a result, there's an almost cinematic quality to the these descriptions, as if a camera is slowly moving through a graveyard, before jumping to a flashback (the "incense-breathing Morn") in the same landscape.