A near-capacity crowd filled New York City’s Town Hall for the Peabody Chamber Orchestra’s April 15 concert there featuring Leon Fleisher as both conductor and pianist. Fleisher, Peabody’s Andrew W. Mellon Chair in Piano, led the orchestra in a reprise of the all-Mozart program they had performed two nights earlier in Peabody’s Miriam A. Friedberg Concert Hall: Mozart’s Symphonies No. 1 and 41, and the Piano Concerto No. 12, which Fleisher led from the keyboard. Presented by the People’s Symphony Concerts of New York, the performance was a celebration of Fleisher’s 90th birthday and nearly 60 years on the faculty at Peabody. It also marked the first appearance by a Peabody ensemble in New York since 2006.