Copyright, which extends for 70 years after an artist's death, exists to protect a creator's property rights and income.Wrong. Copyright does not "exist to protect a creator's property rights and income". It exists to enlarge the public domain. But Strickland's main purpose here is to introduce the topic of debate with the immediately following sentence: "Many argue cultural content should be in the public domain sooner, available to future generations to build upon and freshen."
Indeed, it is the long posthumous period (now 70 years in the U.S.) that can be destructive of an artist's legacy. Simon Hattenstone noted in 1991 that
Britain's most notorious instance of artistic suppression surrounded the comic operas of Gilbert and Sullivan. Until the copyright [in Gilbert's librettos] lapsed in 1961, 50 years after Gilbert's death, the D'Oyly Carte Opera Company held a monopoly on all professional performances of the G&S repertoire. The result was a total mummification of the works: not a note of music could be sung differently...."Hattenstone went on to note that The New Grove held that the expiration of copyright in Gilbert's work "proved Salutary, leading to...an all-round improvement in standards and a reawakening of imaginative interest." (Entry "Sullivan, Arthur", in The New Grove Dictionary of Music and Musicians Vol. 18, at p. 359. The re-written article on Sullivan in The New Grove Second Edition, however, does not contain this statement.)
--Simon Hattenstone, "Keep open the routes to the past", The Times (London), November 5, 1991, Arts p. 14.
Since copyright now lasts so long, a foundation like the Cunningham Dance Foundation will be active for several generations. The second generation might have a different outlook from the first. The third, different from the second. And these successive boards will not always be wise and appreciative of the creative process. In the end, the only way to make sure that Cunningham's dances do not fossilize as Gilbert and Sullivan's operettas are said to have done, is for the copyrights in them to expire.