“New York’s the Big Apple, bub, the heaviest scene in the world” (Rolling Stone magazine, 1969)

Rolling Stone magazine began in New York City in 1967. Although “Big Apple” was popular in jazz music, Rolling Stone mostly reported on rock music.
 
A letter by “Fly Paper” about New York City’s rock scene was published on April 5, 1969:
   
“New York’s the Big Apple, bub, the heaviest scene in the world and now it’s evolved into a ‘Super scene.’”
 
This citation is before the New York Convention and Visitors Bureau repopularized “Big Apple” in the 1970s.

 
Wikipedia: Rolling Stone
Rolling Stone is an American monthly magazine that focuses on music, politics, and popular culture. It was founded in San Francisco, California, in 1967 by Jann Wenner, and the music critic Ralph J. Gleason. It was first known for its coverage of rock music and for political reporting by Hunter S. Thompson.
 
5 April 1969, Rolling Stone (New York, NY), “Correspondence, Love Letters & Advice,” pg. 3, cols. 2-3:
New York’s the Big Apple, bub, the heaviest scene in the world and now it’s evolved into a “Super scene.” Amazingly tight and together. The Groupies in New York are the hip enough not to be elsewhere if you get my far out meaning. Please, an essay on New York.
FLY PAPER
NEW YORK
 
2 March 1972, Rolling Stone (New York, NY), pg. 28, col. 1:
Recording Scene
In the Big Apple
 
30 March 1972,  Rolling Stone (New York, NY),  “Blue Oyster Cult” album review by Lester Bangs, pg. 54, col. 5:
But the Big Apple, as us farmboys call it, hasn’t really come through with solid rockout organizations too often.
 
17 August 1972,  Rolling Stone (New York, NY), pg. 6, col. 1:
Jazz Explosion
Shakes Big Apple