Although Micheelsen is recognized in Germany as a distinguished composer involved with the "renewal and rejuvenation" of sacred music in the first half of the twentieth century, little of his music is known to American choral conductors. (Only two of his pieces are presently published in English by an American publishing company.) The purpose of this study is to document Micheelsen's role as a composer, performer and educator in Germany since the mid-thirties and to make a detailed study of the compositional style and technique used in his sacred choral works.Micheelsen's first creative period (1930-1945) developed from his experience as a student connected with the Singing Movement, the Schutz Movement, the Liturgical Movement and his work with Paul Hindemith. Although Micheelsen looked to the past for inspiration, he tried to imbue his music with the spirit of his own time. He continually stressed the need to look forward in art and welcomed new music that was stylistically compatible with older styles.The second creative period (1945-1973) shows the influences of the many new styles prevalent in Germany after World War II. These influences can be seen in Micheelsen's increased use of all twelve tones of the chromatic scale, an increase in his use of chromaticism and larger vocal ranges, and his experiments with serialism.Micheelsen carried on the developments of the renewal in sacred music as the Director of the Church Music School in Hamburg and as Department Chairman of the Sacred Music Department in the Hamburg Hochschule fur Music. Until his retirement in 1962, Picheelsen was a leader in the education of church musicians and in the rebuilding of musical life in Germany after.the Second World War.In all his creative work, Micheelsen maintained a commitment to a style of music which emphasized melodic (linear) elements as a basis for composition. He placed a great emphasis on the relationships of text and music. His technique recalls, but does not copy, the contrapuntal style of Renaissance vocal music and puts vocal technique at the center of all his music.