Composer and lyricist Irving Berlin made the Great American Songbook a whole lot richer with tunes like “White Christmas” and “Cheek to Cheek.” His music was deceptively simple, often written in the vernacular of the day. Nevertheless, he’s been lauded as one the best songwriters American history.  Big shoes to fill, but ones that actor, playwright and pianist Hershey Felder does in his one-man show now playing at Chicago’s Royal George Theatre.  Earlier in his career, Felder played other 20th-century music men George Gershwin and Leonard Bernstein, so the sounds of Irving Berlin are right in his wheelhouse. Tony Sarabia sits down with Hershey Felder for a chat and a performance.