What passing-bells for these who die as cattle?

The tone of the first stanza of Owen's "Anthem for Doomed Youth" is crystallized in the first line, above. Borrowing from Edmund Spenser's genius, the consonants establish the tone with clarity.

Remembering that in British English the articulation of /t/ involves a brisk plosive sound with an aspiration made at the back of the teeth, note the line opens and ends with /t/ in "what" and "cattle." This is meaningful because the beginning and ending /t/ carries with it a biting tone that is heightened by the /d/ in "die." The plosive emphasis is echoed elsewhere as in "Only the stuttering rifles' rapid rattle." Therefore it may be said that the tone in the first stanza is one of bitterness overlying sorrow, a sorrow that is shown in lines without plosives:

Only the monstrous anger of the guns. ...
Nor any voice of mourning save the choirs,—

The first line of the second stanza indicates a change in tone as it ends with emphasis on the vowel sound in /all/. While plosives remain a feature, the plosives of choice are more often muted voiced /d/ rather than biting unvoiced /t/:

And each slow dusk a drawing-down of blinds.

The softening emphasis on vowels throughout, as in "Shall shine the holy glimmers of good-byes" plus the muted /d/ plosive indicate that the tone has shifted from (1) bitterness in sorrow to (2) overriding sadness. The text equally shits emphasis from "hasty orisons"--that which demarcates the funeral of the soldiers--to "The pallor of girls' brows shall be their pall," which demarcates the deceased soldiers' own experience (though they be dead). Thus the tone in the second stanza is one of sadness and contrasts with the bitter tone of the first stanza.