Dialect coach Sam Chwat, who helped actors and others gain or lose regional accents, as necessary, through his Sam Chwat Speech Center in Manhattan, died March 3 in Manhasset, Long Island, of lymphoma. He was 57.

When Julia Roberts needed to tone down her Southern speech or Tony Danza his New York accent, Chwat helped them. He also trained Robert De Niro with his Southern drawl for “Cape Fear” and Marcia Gay Harden, who needed a New York accent for her part in “Pollock.” Other thesps included Willem Dafoe for his role as Max Schreck, a German actor who’s secretly a vampire, in “Shadow of the Vampire”; and Olympia Dukakis, who played a Holocaust survivor in her one-woman show “Rose.”

Samuel Elliott Chwat earned a master’s in speech pathology from Columbia U. Teachers College in 1977. After several years of traditional work treating lisps and stutters, he began to help those who felt hindered by their accents.

Roberts, a Georgia native, was an early client.

Chwat is survived by his wife, Susan Lazarus Chwat; three daughters; and a sister.