Is there a reason why both pieces are together?

[faa2010]

I have been listening the International Fryderyk Chopin Competition, and something got into my mind (apart from wanting to learn the Andante spianato)

Why the Andante spianato and Grande Polonaise in E flat major op. 22 are played together? I know Andante spianato is the introductory part, but in other videos, apart from the scores, that both are treated like separated pieces.  Was there a reason when Chopin composed both of them? What's the story behind those pieces?

[birba]

The polonaise came before the andante spianato.  It was a piano and orchestra piece.  Afterwards, he wrote the andante spianato to go with the polonaise as a solo piano piece.

[stevebob]

As birba says, the polonaise was composed a few years before the Andante spianato (ca. 1830 and 1834, respectively).  They were published together in 1836 as "Grande Polonaise Brillante précédée d'un Andante Spianato pour le Piano avec accompagnement d'Orchestre,” which is slightly misleading:  the orchestral accompaniment is for the polonaise, while the Andante that introduces it is a piano solo.

There’s evidence that Chopin performed the Andante spianato independently of the polonaise, but I haven’t found information about why he chose to couple the two pieces for publication.  I, too, would be interested in the answer to that question