From 1922 through 1947, Whitehead was organist-choirmaster of Christ Church Cathedral. There he "became the acknowledged leader of Montreal's Protestant church music scene." In 1936, Wilfrid Pelletier invited Whitehead's Cathedral Singers to perform with the Montreal Symphony Orchestra for the opening of the very first Montreal Festivals. Thereafter, Whitehead prepared the festival choruses for performances of Johann Sebastian Bach's "St Matthew Passion" and Ludwig van Beethoven's "Symphony No. 9", Bach's "Mass in B Minor", Giuseppe Verdi's "Requiem", and Beethoven's "Missa solemnis".