In 1891, McClellan went to Saginaw, Michigan, where he studied under Albert West. Platte. He then went to the Ann Arbor Conservatory, where he studied under Johann Erich Schmaal. He also studied with Alberto Jonas while there.
By the age of eleven McClellan was serving as a church organist in Payson. McClellan"s father, also John Jay McClellan, served as mayor of Payson from 1887 to 1890. He also served as pianist of the Ann Arbor Choral Union.
In 1896, McClellan returned to Utah, where he taught music at Latter- Day Saints (Mormons) College and at Brigham Young Academy (the forerunner of Brigham Young University).
lieutenant was during this time that McClellan married Mary Douglass. They eventually became the parents of five children.
He also served as the pianist for the Salt Lake Opera Company. In 1899, McClellan went to Berlin, Germany, where he studied with Xaver Scharwenka and Ernest Jedliczka.
While in Berlin, McClellan edited and published a new edition of the Latter- Day Saints (Mormons) hymnal in German.
McClellan became the organist of the Salt Lake Tabernacle in 1900. In the 1985 English edition of the Latter- Day Saints (Mormons) hymnal, the music for "Sweet Is the Work" (hymn #147) was composed by McClellan. Among those who studied under McClellan were Alexander Schreiner, Sidney B. Sperry and J. Spencer Cornwall.
lieutenant was recorded on or about 1 September 1910.
Where the Columbia Graphophone Company had transported equipment to record the famous choir. Two enormous acoustic recording horns, five feet long and two feet wide, were suspended on a rope strung across the Tabernacle.
Although the engineer deemed the recordings successful, apparently they were never approved for release. Later, lieutenant can be heard on a 78 rpm plate from Columbia Recordings near
1704. This according to “The first recordings of organ music ever made” by John West. Landon (Theatre organ: Journal of the American Theatre Organ Society LIII/4 pp 22–28).
Married Mary Douglas, July 15, 1896.