I turned back to Heaney, like an old trusted friend, to see what I could learn about lyric poetry, and found this excerpt compelling:
... there is another kind of adequacy which is specific to lyric poetry. This has to do with the 'temple inside our hearing' which the passage of the poem calls into being. It is an adequacy deriving from what Mandelstam called 'the steadfastness of speech articulation', from the resolution and independence which the entirely realized poem sponsors. It has as much to do with the energy released by linguistic fission and fusion, with the buoyancy generated by cadence and tone and rhyme and stanza, as it has to do with the poem's concerns or the poet's truthfulness. In fact, in lyric poetry, truthfulness becomes recognizable as a ring of truth within the medium itself. And it is the unappeasable pursuit of this note, a note tuned to its most extreme in Emily Dickinson and Paul Celan and orchestrated to its most opulent in John Keats, it is this which keeps the poet's ear straining to hear the totally persuasive voice behind all the other informing voices.
It would seem Heaney is advocating, to alter Dickinson's famous quote, that poets can only "tell all the truth by telling it slant." Or, as Ella Fitzgerald has been wailing at me through speakers of the coffee shop in which I find myself typing this now, "It don't mean a thing if it ain't got that swing."