Frédéric Chopin wrote his Waltz for piano in A minor sometime between 1843 and 1848. It was published over 100 years later, in 1955, thus lacking an opus number. Because of this, it is often designated by its Brown catalogue number, B. 150. It is a piece with a strong folkloric component, both in the harmonic progression and the form. Marked Alegretto, it is 56 bars long, and it takes around two minutes to be performed.