Born in Trenton New Jersey, Coates attended Ewing High School. In 1962 he graduated magna cum laude from Rutgers University where he earned a degree in romance languages. John's musical career progressed quickly early in life. He played local clubs at age fourteen, summers at the Deer Head Inn at age sixteen, and recorded his first LP for Savoy Records while still a senior in high school. He performed on the Steve Mein , Mike Douglas, and Merv Griffin TV shows in support of that album.
His first road gig was with Charlie Ventura with whom he also recorded two albums. He then returned to the Deer Head in 1962 where he has played for almost 50 years.
John was also employed by Shawnee Press as an arranger and editor from 1964 to 1976. Coates' arrangement of "Amazing Grace" has cold more than 750,00 copies and remains one of the publishing company's and Coates' best sellers. Around this time he also recorded eight albums for Omnisound Records under the direction of Yoshio Inomota and began playing across America, Europe, Japan, and Canada promoting his albums
John recorded several albums with Pacific St. Records starting in 1993. He now lives in Mission Viejo California after reuniting with his first wife.