Sculpted in ZBrush, the color texture was painted in Substance Painter, rendered in Maya with Arnold, used Xgen core for the hair. Schubert wasn’t famous during his lifetime and probably couldn’t afford a highly skilled artist to paint his portrait, most of the portraits of him were done decades after his death when his music finally started to make it to the mainstream. All I could find as a reference was just one photo of a cast impression of his life/death mask, unfortunately the original mask is lost or destroyed in the market.