John Garcia Gensel was born in Manatí, Puerto Rico in 1917 and baptized as a Roman Catholic by his birth parents.

At the age of six he was sent alone to the United States, where he was raised in Catawissa, Pennsylvania by his aunt Fina and her husband Charles Gensel, who legally adopted him.

In 1932, John Gensel heard Duke Ellington play at Berwick, Pennsylvania and fell in love with jazz.

[8] In 1968, jazz ministry had become fully established in Saint Peter's Lutheran Church, on Lexington Avenue in New York City.

Gensel also founded "All Nite Soul", a 12-hour jazz jam session held annually in October, starting at 5pm and continuing through the night.

Gensel, including those held in the memory of musicians such as Duke Ellington, Dizzy Gillespie, and John Coltrane.

Dr. Martin Luther King Jr., he held a tribute concert in his honor at Carnegie Hall to benefit Tougaloo College, an African-American institute in Mississippi.

Gensel received an honorary Doctor of Humane Letters from Wagner College in Staten Island, New York.

Gensel, named "The Shepherd (Who Watches Over The Night Flock)"; the piece is part of Duke Ellington's Sacred Concerts.

[17] On September 12, 1999, Saint Peter’s Jazz Vespers introduced a new African-American worship book in the spirit of Rev.