The speaker packs each line of the poem with consonance. The /l/ sound, for instance, rings out clearly in the poem's first two lines:
On longer evenings,
Light, chill and yellow
This repetition of the gentle, liquid /l/ sound makes these lines sound beautiful and smooth but also subdued, setting the pensive tone for the rest of the poem.
Later, the /r/ sound repeats many times in lines 6 and 7:
In the deep bare garden
The multiple /r/ sounds give this section a subtle growl that makes the language feel textured. Coupled with the many instances of sibilance ("serene," "houses," "sings," etc.), this creates a meditative, soothing effect that reflects the calm and peaceful nature of the speaker's immediate surroundings.
Another notable use of consonance comes in lines 16 and 17, when the speaker features the /d/ and /n/ sounds:
Of adult reconciling,
And can understand nothing
The /d/ sound in particular is quite commanding and blunt, an effect that imbues this moment with a certain feeling of impenetrability. In turn, the speaker's language reflects the child's inability to break through the adults' "unusual laughter" and grasp what is actually going on between them.