Otto Olsson's early works can be said to have been influenced by Emil Sjögren (Four Piano Pieces op.2, Adagio and Meditation op.14), but he very soon showed a will of his own, most successfully and grandly manifested in his Symphony (1902) and Requiem opus 13 (1903), two very extensive works which were almost completely ignored until the 1970s and 1980s. The bulk of Olsson's output antedates 1918 and a very large proportion of his works are for the organ. His music bears the unmistakable im press of the French organists and composers Alexandre Guilmant and Charles-Marie Widor, but he also developed into Sweden's foremost contrapuntalist. His music, however, was seldom academically erudite, constituting instead a felicitous union of learning and inspiration.

Otto Olsson's reasons for writing a requiem remain unclear. At twenty-two, he had just completed his studies at the Conservatory and was perhaps eager to try out his newly acquired skills in counterpoint and composition on a large-scale work, combining chorus and orchestra.
Maybe the Requiem was intended as a tribute to his father who died in November 1900. He could very well have been inspired by the requiems of Brahms and Verdi which were performed in Stockholm in April 1900 and December 1901, just when he had started on his own requiem (the score is dated 1901-1903).

This Requiem contains:
- Requiem 6'48
- Kyrie 4'55
- Dies Irae 4'30
- Rex tremendae 3'58
- Recordare 3'56
- Confutatie 4'38
- Domine Jesu Christe 7'32
- Hostias 5'01
- Sanctus 13'55
- Agnus Dei 12'09