Nothing here follows ordinary logic, and the poem doesn't ask you to make it. It begins with a single piece of string, inflated by "imaginary wind," marked with notes like a musical staff, and somehow becoming as fluid as water. Then the string speaks, casually saying "See you later," as if it were leaving a party. From there the poem pans outward: popular sentiments carry on, tall buildings settle into a heavy, "lump" sky, and church music wanders softly into mucus.
The speaker never says how they feel, so the mood comes from the images. It's playful and dreamy, but also a little queasy. The ending in particular pulls something lofty, church music, into something bodily and unpleasant. Judging by the imagery, the poem seems interested in how thin the line is between the delicate and the clumsy, the musical and the physical. It's best read the way you'd listen to a tune: for its sounds and odd turns rather than a tidy message.