The poet Ted Hughes considered the poem sequence an excellent way of getting 'at' the poetry, as though poetry is a rich seam of ore and the poet, through his or her working methods and inspiration, is simply chipping away at the dense rock that covers it.
I've always felt that Hughes's attitude towards the poem sequence indicates that he, like me, needed a bit of a run-up to writing poetry. That cold-calling poetry central is almost guaranteed to result in an engaged tone, or the phone being slammed down on you.
The good stand-alone poem is a miracle. It comes seemingly out of nowhere and finishes in a place no poet can envisage whilst scribbling the first line on the back of an envelope in a crowded train carriage. It doesn't happen often, that astonishing coup de foudre that results in the good one-off poem. Certainly not to a poet like me, anyway.
So in order to generate 'good' poems, to get up a powerful head of steam writing-wise, I tend to work my way gradually towards the poetry through the narrative structure of a sequence. Maybe partway into the sequence, or towards the end of it, I will stumble across a good poem. Or it will find me. And I'll know that it was worth the time and sheer effort involved in building a complicated narrative around it.
That's how my last sequence, Boudicca, evolved, and there are several poems there which work outside the narrative sequence: 'A Handful of Bones', 'Driving the Tribes', 'War Paint', 'History', maybe 'Purification.' Of course, it helps the poet to readily establish the premise of a sequence when the narrative is linked, as Boudicca is, to a well-known historical, legendary or mythological figure or story.
Often a poem like that will lose its peculiar power by being removed from the sequence and examined as a stand-alone poem. But sometimes it won't. And that test is usually one of memorability. Does that one poem stay in the mind long after the sequence around it has been forgotten?
I'm working on a sequence for my third collection. Not a lengthy sequence, at this stage. Maybe 20 poems. The number rises and falls as I cut earlier less-sustainable efforts or insert shiny new works. But it's already yielded two or three poems which might survive their inception to be lifted out of the sequence later and considered as stand-alone pieces.
I also have two other ideas for sequences, with a few poems already written for each. But nothing is decided. Those poems may appear as stand-alones in my third book, simply because the sequence never grew into something workable. Or I may jettison them altogether, perhaps returning to them another year, if I have enough time and it feels right to move back into that territory.
That's the beauty of sequences. They can grow with the poet or be laid aside and returned to, where stand-alone poems are either completely there from the beginning, all of a piece, or they tend never to be quite right. With the sequence, you can fuss and fiddle about under the hood for years, if necessary, without ever losing the initial impetus behind the story. But the stand-alone poem is a more fragile creation; if the initial inspiration dissipates for any reason before the poem can be completed, the poem has often lost its chance of authentic life.
Think of poor Coleridge and that ill-timed knock at the door ...