Chopin had a free sense of rhythm. In 1842, Chopin was giving a lessen to Wilhem von Lenz when Meyerbeer walked in. The Mazurka (op. 33 no. 3) was being played. von Lenz recounts:
“That is two-four time,” said Meyerbeer.
For reply, Chopin made me repeat, and kept time by beating loudly on the instrument with his pencil; his eyes glowed.
“Two-four,” Meyerbeer repeated quietly.
I never but once saw Chopin angry; it was at this time! A delicate flush colored his pale cheeks, and he looked very handsome.
“It is three-four”, he said loudly, he, who always spoke so softly.
“Give it me for a ballet in my opera” – l’Africaine, then kept a secret – ” I will show you, then.”
“It is three-four,”almost screamed Chopin, and played it himself. He played it several times, and stamped time with his foot -he was beside himself! It was of no use; Meyerbeer insisted it was two-four, and they parted in ill humour.
Source: Schonberg, Harold (1987) The Great Pianists. New York: Simon & Schuster, p.153-154.