What is the tone of Eliot's "The Love Song of J. Alfred Prufrock?"

We might describe the tone of Eliot's well-known poem as "bitterly impassive."

Opening the poem with a faux-romantic invitation to explore the contemporary imagination, Eliot compares this little imaginative space to a patient "etherised upon a table."

The modern spirit is, then, conducting an investigation of itself - playing doctor and playing patient. The poet represents the subject and the speaker. Each are affected by the disillusionment of the modern day and each are powerless to escape that disaffectation and so must develop a sense of detachment. We might say that the effort to cultivate this detachment is, effectively, what the poem is about.

The tone then is ironic, supercilious, bitter, dreamy and romantic all at once. 

The romance comes in the fact that the poem seems to yearn for a time before modernity (because, as the poem outlines, modernity is simply "not enough" to satisfy the spirit). The poem details the many tedious and false aspects of life in (high) society that characterize the modern era (in the 1910s). 

Suggesting that death will come after a life made up of nothing more than these tediums, the poem's narration takes on an ironic distance from the tea parties, the dinner conversations, the decisions about how to wear one's hair, etc. Yet, despite the ironic distance and the attempted emotional distance, the poet cannot separate himself from that world and, unfortunately, cannot see much redeeming value in that intractable connection. 

"Although he understands the mediocrity of his surroundings and of the society he frequents, he cannot rise above them" (eNotes). 

In such a spiritual crisis (wherein life's meaning is always and only of the pettiest variety), the poet is bitter - at his powerlessness to truly escape, at the double irony of his ironic detachment (he has to look at himself ironically too, knowing that his emotional distance actually implicates him in the emptiness of his social world). 

The speaker in Eliot's poem "The Love Song of J. Alfred Prufrock" is certainly feeling alone. The words chosen for the poem distinctly depict a person feeling forlorned and isolated.

Here are the most prominent words which depict the tone in the poem: etherized, deserted, dying, digress, lonely, silent, tired, wept, old, and drown.

The most prominent fact in regards to the poems lonely tone is the usage of "us" in the first stanza. One could initially believe that the speaker is talking to another person, but the fact is that he is speaking to himself. This solidifies the loneliness that the speaker is feeling.

The speaker is certainly feeling as if his (assumptive based upon Eliot being a man) life is completely uncertain. He knows he is growing older, and that fact scares him. Therefore, his tone (the speaker's ) seems to be one in which he has lost hope in life and finding another person to share his life with.

What is your interpretation of the title of T. S. Eliot's The Love Song of J. Alfred Prufrock?

The title of The Love Song of J. Alfred Prufrock by T. S. Eliot itself suggests the incongruity of traditional poetic expression with the modern world. The notion of a love song suggests a romantic poem, perhaps along the lines of a Petrarchan sonnet, in which the lover portrays his longing for the beauty and charms of his beloved. On the other hand, the form of the name J. Alfred Prufrock is precisely the opposite of romantic, evoking formal modes of address that might be used in the signature of a business letter or on a business card. This presents to the reader an image not of a romantic youth who is the typical protagonist of love songs, but rather of a rather old fashioned fussy middle-aged man, the character as he is described in the lines:

"My morning coat, my collar mounting firmly to the
     chin,
My necktie rich and modest, but asserted by a
     simple pin ..."

In "The Love Song of J. Alfred Prufrock," how does the tone relate to the subject's presentation?

Certainly this modernist classic opens itself up to a multiplicity of different interpretations. However, one of the meanings that stands out to me is the approach of Alfred Prufrock to time, and the way that time is viewed with fear, trepidation and how this relates to indecision. Centrally, this poem concerns the speaker's fear of committing to a woman and how this will in turn ensnare him in the monotony of social conventions that make up life. Time is shown to be something that is elusive for him and resulting in his premature aging. Note how time is viewed in the third stanza:

There will be time, there will be time
To prepare a face to meet the faces that you meet;
There will be time to murder and create,
A time for all the works and days of hands
That life and drop a question on your plate;
Time for you and time for me,
And time yet for a hundred indecisions,
And for a hundred visions and revisions,
Before the taking of toast and tea.

Note the emphasis on how the speaker is trying to convince himself that "there will be time," shown by the repetition of this phrase. He is trying to convince himself that he doesn't have to commit yet, however at the same time he recognises that time is not infinite, and if he does not commit and make a decision against the "hundred indecisions" that are still open to him, he risks remaining lonely and old forever.

This perhaps explains the somewhat whistful and bleak tone regarding time, and life and how it slips away from us. The indecision of J. Alfred Prufrock is shown to be reflected in the tone of bleak disillusionment with life and society which the speaker seems to be both drawn to out of fear but also to despise.