Music fans at the San Francisco venue Feinstein's at the Nikko were in for a treat on Friday, when Liza Minnelli made a rare, unannounced appearance - and performed a touching tribute to her mother, Judy Garland.

The 70-year-old Oscar winner duetted with Michael Feinstein on "I Love a Piano," theIrving Berlin tune from Garland and Fred Astaire's 1948 film Easter Parade.

Minnelli was introduced to the sold-out crowd by her sister, Lorna Luft, 63, who recently commemorated the 47th anniversary of her mother's death by performing Garland's signature song, "Over the Rainbow," for the very first time ever.

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