This year, visa problems made necessary a large number of casting changes in the in the United States. A normally difficult situation became worse by the failure of the Homeland Security’s computer system. Now, the Boston Globe reported that British composer and conductor Oliver Knussen has been forced to cancel his appearance at the Festival of Contemporary Music in Tanglewood where he was to conduct a memorial program in honour of the composer Gunther Schuller, on Thursday evening. He will be replaced by two conductors, Jonathan Berman and Stefan Asbury.