On the other hand, I do not believe that Chopin wrote to a metronome. There is undoubtedly a sense of music that takes count of the "shape" of the rhythm in a melody rather than of bar divisions, which came rather late in the history of written music and were certainly not the first or most important thing that musicians attempted to record. The creation of such shapes is part of thematic invention. Some musicians have the faculty of invention, rhythmic, melodic. Likewise some poets.
Treatises full of musical notes and of long and short marks have never been convincingly useful. Find a man with thematic invention and all he can say is that he gets what the Celts call a "chune" in his head, and that the words "go into it," or when they don't "go into it" they "stick out and worry him."
You can not force a person to play a musical masterpiece correctly, even by having the notes "correctly" printed on the paper before him; neither can you force a person to feel the movement of poetry, be the metre "regular" or "irregular." I have heard Mr. Yeats trying to read Burns, struggling in vain to fit the "Birks o' Aberfeldy" and "Bonnie Alexander" into the mournful keen of the "Wind among the Reeds." Even in regular metres there are incompatible systems of music.
I have heard the best orchestral conductor in England read poems in free verse, poems in which the rhythm was so faint as to be almost imperceptible. He read them with the author's cadence, with flawless correctness. A distinguished statesman read from the same book, with the intonations of a legal document, paying no attention to the movement inherent in the words before him. I have heard a celebrated Dante scholar and mediæval enthusiast read the sonnets of the "Vita Nuova" as if they were not only prose, but the ignominious prose of a man devoid of emotions: an utter castration.
The leader of orchestra said to me, "There is more for a musician in a few lines with something rough or uneven, such as Byron's
There be none of Beauty's daughters With a magic like thee;
Unless a man can put some thematic invention into _vers libre_, he would perhaps do well to stick to "regular" metres, which have certain chances of being musical from their form, and certain other chances of being musical through his failure in fitting the form. In _vers libre_ his musical chances are but in sensitivity and invention.