He started out initially portraying George Gershwin, which was then joined by Chopin, Beethoven, Leonard Bernstein, Franz Liszt and Irving Berlin and now by “Our Great Tchaikovsky” as Chicago favorite Hershey Felder brings his latest self-created solo musical portrait of yet another legendary composer to Steppenwolf’s Upstairs Theatre through May 15.Many years ago there was another classical pianist named Victor Borge who gained his reputation as “the Clown Prince of Denmark” by performing …