It was Mozart's intention to keep the accompaniment part flexible in his piano concerto in E-flat Major, K. 449 (and in, K. 413–415 as well) as we know from a letter of May 15th, 1784 he wrote to his father: ". . . the concerto in E-flat may be performed a quattro that is, without wind instruments".
The edition is based on Marius Flothuis' Urtext edition, which was published in the Neue Mozart Ausgabe (NMA). in the arrangement for two pianos, the solo part remains unchanged and thus identical with the version in the NMA. The piano reduction adheres to the original orchestral score.