I think the title helps to bring to light the experience of the speaker. The speaker, presumably Wordsworth, gazes upon the open field to see this maiden working in the field. She is alone, without a soul except for the speaker in sight, and this is what triggers the moral imagination of the speaker as her song is the only thing heard. The idea of "the solitary reaper" holds a great deal of significance because the experience of the speaker could not have been amplified to the degree it was if the maiden in the field was surrounded by others. Her song, which is not entirely understood, is one that helps to allow the speaker to ruminate and reflect inwards. The fact that this is a solitary experience driven by a solitary setting makes the title quite appropriate, in my mind.
Wordsqworth's The Solitary Reaper, published in 1805, has an apt title. It is a "mirror image" of "I Wandered Lonely as a Cloud": this poem is also an encounter of sorts, with a distant human being instead of a field of flowers. It is in a real way a mirror image of the daffodils poem. Look at its tenses: where is the poet, and where are we, at the poem's start, and at its finish? There is a reversal of the tenses encountered in "I Wandered Lonely as a Cloud."
As an encounter poem: "The Solitary Reaper" fits, as well, into a genre of poems (Keats's "Ode to a Nightingale" and Wallace Stevens' "The Idea of Order at Key West" are other examples) that record a poet's experience of music, whether from a human or a non-human source. It is natural, of course, for a poet to be interested in music, and we can infer some specific reasons for Wordsworth's experience here. Poetry between music and language: one of the main ideas of the poem is, of course, the poet's attraction to sheer music, a song being sung in a language he cannot understand (Erse or Gaelic). So the solitary reaper is herself de-personified and made into something like a bird.
Subjects of life and death: at the same time, we sense a kind of suggestiveness in her role as a reaper (not grim, certainly, but connected to the harvest). Solitude is also definitely a subject. Perhaps the poem has other possibilities? In fact, once one realizes that the direct address ("Behold," "stop," and so forth) to either the reader or the poet himself echoes the traditional language of epitaph poetry, then we get the sense that Wordsworth is recounting something like an experience from another dimension.
Wordsworth is addressing himself from within himself. He is in a sense reaching toward eternity. Such a dimension is implicit in the poem's commands, its address, its titular figure, its speaker's trouble with understanding her song, the various possibilities he infers for its themes, and above all, by its own use of present and past tenses. She is always singing to him in a continual present, alive, although far away and long ago herself. He hears her song in his heart, like a burden.
But did it happen this way? Unlike "I Wandered Lonely as a Cloud," "The Solitary Reaper" has no autobiographical origin. Wordsworth read a travel account describing the scene. The nature of the "first-person speaker" in a lyric is as much a piece of fiction as any fable the poet can choose to employ. Never assume that it is the poet him- or herself who is actually having the experience, even when the poet is William Wordsworth, whose work is almost always about himself. One can be fooled.
The title then implies a singular person (solitary) who benefits in some way (reap--reaper) from listening to the music.
Yes, the title "The Solitary Reaper" is very apt to the poem.
The poem is made up of four stanzas. In the first stanza, Wordsworth sets the scene for the readers. He asks us to observe the Highland girl busily reaping the ripe grain and singing to herself. He asks us to pause and listen to the song which fills the entire valley,or quietly leave the place without disturbing her.
In the second stanza, Wordsworth tells us that her beautiful song was more refreshing than the melodious song of the nightingale which welcomed the weary travellers as soon as they arrived at an oasis and that her song was more pleasing than the cuckoo's song which signalled the end of the harsh winter season and the beginning of spring.
Wordsworth uses two images--"word pictures"--to describe how refreshing and reinvigorating it was to listen to the melodious song of "the solitary reaper."
1. A group of exhausted travellers when crossing the scorchingly hot Arabian desert arrive at a nearby oasis to refresh themselves. As soon as they enter this cool and shady retreat, they first hear the melodious song of the nightingale and immediately they feel revitalised. The tuneful and pleasant song of the bird drives away all their feelings of exhaustion. Similarly, Wordsworth remarks that he was also revitalised when he heard the "melancholy strain" of 'the solitary reaper.'
2. In England during the bitterly cold winter season all the birds migrate to warmer countries in the tropics. They return to England at the beginning of the spring season which marks the end of winter. Traditionally, it is the cuckoo which first returns to England in spring and as soon as the people hear the melodious sound of the cuckoo bird they are thrilled and delighted because they know that the harsh winter season has ended. The Hebrides are a group of small islands in the remote North West coast of Scotland. The winter season in the "farthest Hebrides" was always extremely harsh and the sound of the cuckoo bird signalling the end of winter was specially significant. In the same manner, the song of the solitary reaper was special to Wordsworth.
Since Wordsworth could not understand Gaelic, the language of the reaper, he impatiently asks whether someone could tell him what she was singing about. By doing so he sparks our imagination as to what she could be singing about.
Will no one tell me what she sings?--
Perhaps the plaintive numbers flow
For old, unhappy, far-off things,
And battles long ago:
Or is it some more humble lay,
Familiar matter of to-day?
Some natural sorrow, loss, or pain,
That has been, and may be again?"
Soon,Wordsworth leaves the scene concluding that although he could not understand what she was singing about nevertheless he could always remember the melodious tune of her song:"The music in my heart I bore/Long after it was heard no more."
Wordsworth wonders whether she is singing about the past - about some sorrowful incident of the past, like a defeat in a battle OR about some unhappy incident in the present which may be repeated again in the future. The important thing to remember is that whether it is the past, the present or the future Wordsworth is convinced that what she is thinking about is sad and sorrowful which is echoed in the melancholic tone of her melody.
The words 'single' 'solitary' and 'alone' have been foregrounded. 'Single'implies that she is the only person in the valley; 'solitary' hints at the melancholy mood of the poem and 'alone' refers to the fact that there is no one to help her.