Jean de Reszke can be heard on a number of Mapleson Cylinders

Mediafire link for Mapleson cylinders

(These are zip files – left click the link, download the files, then unzip when downloaded)

As the LP notes, this is not high-fidelity sound. This is IRCC LP7006, issued in 1955, containing transfers of a number of Mapleson Cylinders, recorded live from the stage of the Metropolitan Opera House from 1901 to 1903.

de Reszke appears on the following tracks:

8. Wagner – Siegfried – Ho-ho! Ho-hei! (Act 1)
Andreas Dippel, tenor; Albert Reiss, tenor. Walter Damrosch, conductor
4/3/1902
(Sleeve notes attribute to Jean de Reszke, and Alfred von Hübbenet, 19th March 1901, conducted by Walter Damrosch)

14. Meyerbeer – L’Africaine – Duet, Act 4 (Three fragments)
Lucienne Bréval, soprano; Jean de Reszke, tenor. Philippe Flon, conductor
15/3/1901