A group of the finest young professional classical musicians based out of Carnegie Hall is returning for their biannual residency at Skidmore College, now in its 18th year. Their Oct. 25 performance at Skidmore’s Arthur Zankel Music Center, occurring at the end of the five-day residency, will spotlight the music of South Africa. It begins at 7:30pm that night in the Helen Filene Ladd Concert Hall.