Summer in New York includes Lincoln Center's annual "Mostly Mozart Festival" (July 29-August 24), and it is a pity that so many events were cancelled as a result of a labor dispute involving the Mostly Mozart Festival Orchestra. However, many events were retained, and the dispute has been settled, but apparently too late to result in rescheduling.One of the programs that survived was the August 5th concert by the Scottish Chamber Orchestra, making its Mostly Mozart debut under the baton of Joseph Swensen at Avery Fisher Hall. It was a program well-received by an enthusiastic audience. The program opened with the overture to Der Schauspieldirector. K486, which Mozart composed in 1786 at the request of Austrian Emperor Joseph II, who wanted a work on the subject of opera. (He had also asked for a similar work from Antonio Salieri.) Pianist Imogen Cooper was featured with the chamber orchestra's performance of Mozart's Piano Concerto No.18 in B-flat major, K456, which Mozart is believed to have written in 1784 for a young blind pianist, Maria Theresa von Paradis. Another highlight was baritone Wolfgang Holzmair's singing of "Songs of a Wayfarer," the text written by Gustav Mahler and set to a musical arrangement by Arnold Schoenberg. Holzmair received the most enthusiastic of the evening's ovations. The program was concluded with the Scottish Chamber Orchestra performing Schubert's Symphony No. 3 in D major, D.200. For information about the remaining available programs in the festival, phone 212-875-5030.