He began his formal study every Thursday traveling from Trenton to New York City at age eight with Urana Clarke at the Mannes College of Music on full scholarship.

On Wednesdays, from age 11 to 14, John would play clarinet with his father at the Trenton YMCA dance hall night, where he learned to improvise.

At age 16, Coates was asked to play six nights a week during the summer at the Deer Head Inn, where he lived and ate dinner with the proprietors, Bob and Fey Lehr.

From 1956 to 1958 he toured with Charlie Ventura playing clubs like Birdland, Small's Paradise, the Blue Note, the Brass Rail, and The Flame among others.

After Ventura and while in college John played with Barry Miles, Eddie Gomez, Ron Carter, Woody Shaw, Harry Leahey, Al Cohn, Zoot Sims, Kal Winding, Urbie Green, and Pepper Adams.

At Henderson's he played with Coleman Hawkins, Clark Terry, Doc Severinsen, Phil Woods, Marvin Stamm and Bill Watrous among others.