Why dodecaphony?

During their final years both Igor Stravinsky and Aaron Copland turned to dodecaphony. Even though 12-tone Stravinsky still sounds like Stravinsky, ditto Copland, why did these two masters jump the fence, so to speak?

Jeremy Eichler suggests a cogent possibility: "Copland's 12-tone shift can be compared with his 1920's embrace of jazz: both were styles that felt fresh to him at the time and helped him generate new compositional ideas. Copland saw the 12-tone music not as a readical departure but only as a different 'angle of vision.'"

The adopting of dodecaphony by these two 20th-century masters was a triumph, not only for the technique devised by Arnold Schoenberg (shown above), but also for its adherents. Schoenberg, it seemed, had prevailed.

The decline of dodecaphony's hegemony began not long afterwards.

Dodecaphony: see http://en.wikipedia.org/wiki/Twelve-tone_technique.
Eichler article: see http://www.nytimes.com/2005/08/24/arts/music/24bard.html