He admired composers who involved national folk-culture in their music, e.g. Heitor Villa-Lobos, Carlos Chávez, William Grant Still, Antonín Dvořák and Béla Bartók.
Many of McKay's symphonic works center on folk themes and include pieces dedicated to Native American music.
He was famous for his intellectual and moral support of young composers who studied with him in Seattle, such as William Bolcom, Goddard Lieberson and Earl Robinson.
Some of his early orchestral works attracted conductors such as Leopold Stokowski, Sir Thomas Beecham, Arthur Benjamin, Karl Krueger, Fabien Sevitsky and Howard Hanson for live performances in the 1930s and 1940s.
McKay later authored a poignant article concerning Sinding's time in America for Etude Magazine (November 1944 issue).
McKay began a four-decade tenure of composing, teaching and leading performing groups in concerts of contemporary and American works in the Seattle metropolitan area.
McKay himself was awarded a Guggenheim Grant to study in Europe in the 1920s but turned it down to stay in touch with his American musical roots and to care for his growing young family.
His early teaching assignments took him to North Carolina, South Dakota and Missouri before he finally settled in Seattle; and he composed music celebrating all these locations.
McKay's music is currently recorded professionally by NAXOS on four albums, including two symphonic CDs conducted by John McLaughlin Williams.
McKay's symphonic work "From the Black Hills" was conducted by Howard Hanson at the First American Composers Festival in 1925 in Rochester, N.Y. McKay held the Alchin Chair of Music at the University of Southern California in the summer of 1939, succeeding Arnold Schoenberg and Howard Hanson in that capacity, and returned to teach at USC for two more visiting sessions in later years.
He led a community chamber orchestra in Seattle in the 1930s and occasionally conducted the University of Washington Symphony during his tenure at the School of Music (1927–1968).