“In 2009-10 the Chamber Music Society [of Lincoln Center] gave 35 concerts along with 31 tour dates; the 2014-15 season boasts 54 concerts at home and 68 on tour. … Over the past five years their endowment has risen to $37 million from $31 million; contributor income is up 88%, and subscription sales have increased by 31%.” Stuart Isacoff looks at how they do it.