Olsson used his strong background in counterpoint, combined with an affinity for French organ music, to develop his late Romantic style of composition. He also had an interest in early music and, though not a Catholic but a Lutheran, used the plainchant techniques of Gregorian chant in his Gregorianska melodier. At times he explored polytonality in his output, an advancement not found in other Swedish compositions of the time. In addition to many fine pieces for the organ, he produced various choral works, the most often performed of which is his setting of the Te Deum, which requires not only chorus but stringorchestra, harp, and organ.
As a teacher, Olsson influenced many Swedish musicians (especially church musicians), and he was important in the development of church music in Sweden, which had suffered a long period of decline before 1900. His activities included serving as a member of official committees that supervised the liturgy and hymnology. He also composed Psalm settings for congregational use and wrote two instructional books, on the art of choral singing and psalm singing respectively.[3]
He died in Stockholm in 1964, aged 84.
Works
Choral
Advents och julsånger, for mixed choir and organ (1917)
Advent
Julsång
Gammal julvisa
Davids 121 psalm
Nyårspsalm
Guds Son är fødd (bearbetning af folkvisa)
Det brinner en stjärna i Österland
Jungfru Marias lovsång
Gregorianska melodier (Six Gregorian Melodies), Op. 30 (1910)
Sex latinska hymner (Six Latin Hymns), for a cappella choir, Op. 40 (1919)