https://en.wikisource.org/wiki/Postface_to_114_Songs/Postface_to_114_Songs

"Some of the songs in this book, particularly among the later ones, cannot be sung; and if they could, perhaps might prefer, if they had a say, to remain as they are; that is, "in the leaf"—and that they will remain in this peaceful state is more than presumable. An excuse (if none of the above are good enough) for their existence which suggests itself at this point is that a song has a few rights, the same as other ordinary citizens. If it feels like walking along the left-hand side of the street, passing the door of physiology or sitting on the curb, why not let it? If it feels like kicking over an ash can, a poet's castle, or the prosodic law, will you stop it? Must it always be a polite triad, a "breve gaudium," a ribbon to match the voice? Should it not be free at times from the dominion of the thorax, the diaphragm, the ear, and other points of interest? If it wants to beat around in the valley, to throw stones up the pyramids, or to sleep in the park, should it not have some immunity from a Nemesis, a Rameses or a policeman? Should it not have a chance to sing to itself, if it can sing?—to enjoy itself without making a bow, if it can't make a bow?—to swim around in any ocean, if it can swim, without having to swallow "hook and bait," or being sunk by an operatic greyhound? If it happens to feel like trying to fly where humans cannot fly, to sing what cannot be sung, to walk in a cave on all fours, or to tighten up its girth in blind hope and faith and try to scale mountains that are not, who shall stop it?"