TV SPOTS Remembering Rubinstein For some children, getting to know their father — if it happens at all — comes through honest conversation. For actor John Rubinstein, it came through watching his late father play the piano, which he says provided "an absolutely pure knowledge of a person’s soul.” It’s one of the many insights in tonight’s documentary about John’s late father, Arthur Rubinstein, airing in PBS’ "American Masters” series. Much of "Rubinstein Remembers” (WNET / 13 at 9; WLIW121 Friday at 9) spins off a visit made by the Rubinstein family earlier this year to Lodz, Poland, which was Arthur’s birthplace. With the aid of John’s narration, old photos and film clips take viewers through Arthur’s early years as John Rubinstein a musical prodigy, his Paris playboy days where his buddies were Picasso and Cocteau, his points of despair, and his years of world preeminence. There’s also footage of Arthur talking in new and old clips, and illustrating his remarks on the keyboard. Next month, "American Masters” will repeat the three "Unknown Chaplin” programs, an acclaimed analysis of Charlie Chaplin’s career that included previously unseen footage of the silent-film comedian. The shows hagin Aug. 3. Other August programs will spotligm George Gershwin and Maurice SanAtk Tonight 9:00 PM ® CD AMERICAN MASTERS. “Ru­ binstein Remembered: A 100th Anniversary Tri­ bute." Classical pianist Arthur Rubinstein (photo right) is given a loving tribute by his son, actor and musician John Rubinstein (photo). Filmed in part in Lodz, Poland, Rubinstein’s birthplace. Also shown on ® Friday at 9 pm (60 min.).