I am not sure where talk about the "Big Five" American orchestras originated. The closest I have come to a clue seems to be the February 22, 1963 issue of Time magazine. This was the issue that featured George Szell on the cover and included a sidebar entitled "The Top U.S. Orchestras." It had the following opening sentence:
The five major American orchestras are by general consent the Boston, Philadelphia, New York, Cleveland and Chicago.
I was still in high school when this article appeared; but I had already begun serious record collecting, motivated heavily by what I could hear on WFLN, Philadelphia's only classical music station. I had never heard that America had five major orchestras, by "general consent" or on any other authority. I obviously thought the Philadelphia Orchestra was pretty important, but I also watched the New York Philharmonic on television whenever I had the opportunity. Also, WFLN broadcast the subscription concert performances by both the Philadelphia Orchestra and the New York Philharmonic. When I entered MIT as a freshman, I knew more than a bit about the Boston Symphony Orchestra and even had the Munch-Primrose recording of Harold in Italy in my collection. On the other hand, while I certainly knew about the Chicago Symphony through my radio listening, I never gave it much thought; and, for all that I knew about Szell's reputation, Cleveland seemed pretty remote to someone who had never ventured very far from the Atlantic coast. (I knew a bit more about Chicago because I had been taken to visit relatives in Los Angeles, and our flight stopped there.)
On the other hand, as a record collector, I was well aware that these were far from the only important orchestras in the United States. Much of my interest in modern music was nurtured (for better or worse) by the Mercury recordings made by Howard Hanson with the Eastman-Rochester Symphony Orchestra. That struck me as a pretty important ensemble, even if I had never heard them perform anything by Ludwig van Beethoven. Mercury was also recording Antal Dorati conducting in Minneapolis, and those recordings also attracted my attention. Then there was Maurice Abravanel in Salt Lake City and William Steinberg in Pittsburgh. It had never occurred to me that anyone would want to rank-order these institutions; but I had come to assume that a country with so large a land mass was bound to have a healthy number of orchestras distributed across its states.
So was there really a "general consent" that five orchestras were clustered at the top of the pile; and, if that consent did not exist, what motivated Time to "manufacture" (as Noam Chomsky would put it) such a consent? The answer to that question may lie with the business side of recording and distributing classical music. At the time when the Szell issue of Time appeared, those five orchestras were shared across two major labels, Columbia (Philadelphia, New York, and Cleveland, through the Epic division) and RCA (Boston and Chicago, with Philadelphia having previously recorded with RCA). Thus, I would suggest that the Time sidebar had less to do with ranking orchestras and more to do with a hegemonic agreement between these two major corporations to dominate the market for recorded classical music. In other words the real "manufactured consent" was that "it is not worth listening to unless it has been recorded by Columbia or RCA."
I suppose there is a certain amount of poetic justice in the fact that all five of those orchestras have outlived those corporations, both of which have now been sucked into conglomerate enterprises and have pretty much lost any identities they ever possessed. Meanwhile, however harsh the economy may be, plenty of other American cities (including San Francisco) are supporting symphony orchestras. Indeed, in the absence of any prestige associated with recording labels, the San Francisco Symphony has done very well (to the point of winning Grammys) by distributing recordings of the symphonies of Gustav Mahler through their own label. Thus, anyone who still believes that this is a country of five major orchestras most likely had his/her mind warped by Time in 1963 and has not yet succeeded in unwarping it. I do not agree with everything Chomsky has published; but I think I go along with his opinion that "manufactured consent" tends to be very strong stuff, perhaps even stronger when it turns out to be nothing more than myth!