While sitting under a plum tree in the garden of his house, in Hampstead, Keats stroked with an idea to compose a poem called “Ode to a Nightingale.” He has inspired the song that nightingale was singing. The poet composed the poem keeping in mind the melodious voice of a nightingale, and the mood of the poem was melancholic. Song of Nightingale is compared with Lethe river water as he was feeling that he was happy and forgot about death, as he was fully mesmerized by her song.