Robert Browning incorporated the phrase "each to each" in more than one of his poems. When I came across those three words in Meeting at Night (a poem he published in 1845; I rediscovered it a while ago in the Cambridge Editions' Poetical Works of Robert Browning, published 1974, edited by G. Robert Stange) I heard in my mind, as if someone had pronounced the words, "I heard the mermaids singing, each to each" from T.S. Eliot's The Love Song of Alfred J. Prufrock (1915).
Then I began to wonder if the word coincidence could be applied to the fact that Browning is in the middle of some sentences about sand, coves, waves, and beaches, while Eliot is mentioning mermaids, crabs, beaches, and waves, and that the action in each poem is the opposite of the action in the other one, Browning's narrator travelling across the sea and crossing fields to meet the person he loves, while Alfred J. Prufrock is so strangled by indecisiveness that he can't make himself step across a dry doorway and say hello to the women in front of him: not strangers, he knows them.
He worries about conversation, "And should I then presume? / And how should I begin?", but Browning's narrator is eager, he thinks that speech is less important than the material encounter --
A tap at the pane, the quick sharp scratch
And blue spurt of a lighted match,
And a voice less loud, thro' its joys and fears,
Than the two hearts beating each to each!
-- the encounter will solve everything if there was anything to solve, this point of view more described but also more doubtful in a poem Browning wrote and published nearly three decades later Fifine at the Fair (1872) (and he brings up the same point in other poems along the way so might as well assume it was a constant idea). The Fifine narrator concludes that the important thing between people is the glance or active encounter (there's that Victorian faith in eyes, glances, and orbs, a British faith and not only a British one, "It was a fatal glance she gave him with her Aldebaran-like eyes," writes Hugo in The Man Who Laughs, as translated by someone anonymous, and Chrétien de Troyes was using the eyes as long ago as the twelfth century: "The eyes, which channel love and send the message to the heart, renewed themselves with looking" he wrote in Erec and Eneide, which was Englished by Carleton W. Carroll and published by Penguin) -- "to me, one glance / Was worth whole histories of noisy utterances," writes Browning in Fifine but qualifies himself, "At least, to me in dream," since the narrator at this point is explaining a dream of masked Venetians.
Fifine (two thousand four hundred and sixty-three lines), which is longer than Meeting (twelve lines), gives Browning more room to doubt and explain but since he himself chooses the length of the poem (whether this is conscious or subconscious, never mind which for the moment: the poem itself dictating the length of the poem perhaps, this fits, this doesn't: here, it's done, no more now, rhythm subsiding, finishing, gone slack, ended, says the subconscious to the hand with the pen, whereat the poet surfaces and blinks) conclude that he didn't want doubt in Meeting at Night and did want it in Fifine, and guess for one moment that doubt developed in him as he aged. Call it a theory: doubt began to seem necessary, he had written The Ring and the Book (1868 - 69), a poem two hundred pages long in this Poetical Works, small font, double column on each page; and it spends its length moving from one point of view to another around the subject matter of a triple homicide, encouraging the reader to doubt, since the opinion you are reading at any given moment might be contradicted later.
Nothing is ordained, suggests this poem: a small change could have changed everything, say the characters, people do not understand you, explains the poet. The elderly Pope who orders the murderer's execution goes on for pages reasoning out his decision to himself, the good, the evil, and the possible outcome -- weighing it out -- but no one else in the poem has the faintest idea of the work he's put in: they assume the sentence of death was the one-second spiteful careless spasm of an old man who was going to die himself pretty soon. I notice also, in Prufrock, that the reader is asked to believe that the women in the room will never know or care about the intricacies of the man's thoughts, instead they will be satisfied if they can judge him by his hair and legs.