The scene is outside a tenement on New York's Lower East Side, sometime around 1912. A crew of workers, with block and tackle, is hoisting a piano to one of the upper floors, past a store sign that reads "M. Gershwin: Cigars, Tobacco."

"Ma," asks a little girl, "who's getting a piano?" "It's the Goishwins," replies a heavily accented, matronly voice.

For a moment, seeing this scene from a long-ago Hollywood biography, you may wonder how the directors of the PBS "American Masters" series managed to have a sound camera on hand to record the fateful arrival of George Gershwin's predestined instrument.

In "George Gershwin Remembered" (on Channel 22 at 9 tonight and on Channel 26 next Monday), fictional footage blends smoothly with authentic material, making the show more of a docudrama than a strict documentary. And the otherwise excellent narration should probably have made it clearer, particularly in the early segments. But in any category, this is a dazzling production. And the clever use of fictionalized material adds significantly to the dazzle.

There is quite a bit of the real Gershwin on film, taken from home movies, promotional shorts, etc., and well used in this production. Authentic footage includes long sequences filmed at rehearsals for "Strike Up the Band" and the original production of "Porgy and Bess," and the moving pictures are supplemented with deftly used stills. There are also some interesting home movies that show him playing the piano, clowning and relaxing at parties. But some of the best material comes from a fictional movie treatment of his childhood where the atmosphere of the Lower East Side at the turn of the century is marvelously captured.

Fiction undoubtedly comes close to reality when the camera zooms in on a relentlessly ticking metronome and his first teacher introduces young George to scales and exercises for 50 cents a lesson. Then, almost before we know it, Gershwin (still in his teens) is plunged into the heart of Tin Pan Alley, surrounded by a half dozen competing song-pluggers simultaneously and cacophonously selling half a dozen different tunes. And viewers are plunged in with him. It's vivid, and it gives a fair idea of how it really was.

Gershwin was only 38 when he died 50 years ago this summer, and a lot of his friends and colleagues were still available to talk about him for this production. They tell of a gregarious man who was also a loner, a man who loved women but "could never give himself entirely." Mabel Schirmer, who knew him well, sums it up: "Maybe he had too many women; you know, they followed him all over the place. He came home usually with two or three women from a party. They just followed him home."

The treatment of Gershwin's music is even more effective in some ways than that of his life. Performers seen in vintage performances include Fred Astaire, Gene Kelly, Ginger Rogers, Ella Fitzgerald, Judy Garland and Mickey Rooney -- not to mention Paul Whiteman, who commissioned "Rhapsody in Blue" and is shown conducting it.

The best of many good segments is probably the one near the end dealing with "Porgy and Bess." Todd Duncan, the first Porgy, is still able to sound impressive in a few measures of "Bess, you is my woman now." His recollections of the opera's origins are priceless and well presented, along with home movies of rehearsals for the first production and snippets from several later productions.

Virgil Thomson, who panned "Porgy and Bess" on its opening night, is featured in a commentary that still sounds rather defensive more than half a century later. Other commentary and analysis is provided by Leonard Bernstein and (more usefully) by Michael Tilson Thomas. Best of all the commentators is cabaret singer Michael Feinstein, who worked for six years with George Gershwin's lyricist brother Ira and who has a fine knack for explaining to a nonspecialized audience exactly what it is that makes George Gershwin's music unique.