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Significant as it is that the Manhattan Transfer has been around for 40 years, it is far more remarkable that those four decades have been marked by near-continuous artistic expansion and advancement.
The Four Freshmen and the Hi-Los can statistically claim greater longevity, but the Manhattan Transfer must rightfully be credited as the most enduringly creative vocal group in jazz history.
December(?) 2009, Christopher Loudon
http://jazztimes.com/articles/25275-the-chick-corea-songbook-the-manhattan-transfer