A truly fascinating historical piano recording is this June 28, 1938 recording of Chopin's famous Nocturne in E-Flat Major Op.9 No.2 'with authentic variants' played by Raoul Koczalski, who studied with Chopin's pupil Karol Mikuli.
As a young child, Koczalski famously had lessons with Chopin's pupil Karol Mikuli over the course of four consecutive summers from 1892 to 1895, but he had trained with a number of teachers: Julian Gadomski, Ludwig Marek, and Henryk Jarecki. Some have sought to minimize the extent to which he studied with Mikuli but Koczalski detailed the extent of their work together, noting that "it was no mere trifle: each lesson lasted two full hours and these were daily lessons. I was never permitted to work alone...Nothing was neglected: posture at the piano, fingertips, use of the pedal, legato playing, staccato, portato, octave passages, fiorituras, phrase structure, the singing tone of a musical line, dynamic contrasts, rhythm, and above all the care for authenticity with which Chopin's works must be approached. Here there is no camouflage, no cheap rubato, and no languishing or useless contortions."
As Donald Manildi states in his superb liner notes to the Marston Records release of Koczalski recordings (this reading appears in Volume 2), "The added embellishments and other alterations to Chopin’s melodic writing are said to have been notated by Mikuli after hearing Chopin himself play this Nocturne. (The ornamentation can also be traced to other reliable sources.) ... In light of Chopin’s well-known admiration for bel canto singing, especially from such artists of his day as Guiditta Pasta in the operas of Bellini and Donizetti, it is not difficult to trace the inspiration for the fioritura and melodic ornamentation that are found especially in his nocturnes. We also have reliable accounts of Chopin privately playing nocturnes by John Field and improvising embellishments to enhance Field’s relatively sparse textures. Perhaps the variants in Op. 9, No. 2 originated as a spontaneous jeu d’esprit on Chopin’s part, but in any case they suggest opportunities for creative interpreters to follow Chopin’s practice in similar contexts."
Certainly this raises the question about fidelity to the text and whether the printed version was meant to be the composer's final say about the work (I don't believe it was and there's plenty of evidence indicating that many composers felt the same way). And I am not suggesting that one emulate this particular reading - I don't think one can, not having been trained in the same culture or tradition - nor that this is exactly how Chopin would have played it, but this recording is certainly is worth hearing and studying. It is a fascinating performance that features sumptuous tone, beautiful pedalling, and sensitive dynamic and tonal shadings from a pianist who had lessons with one of Chopin's pupils at a very young age, which surely made a very lasting impression on him.