Oscar (P. Oswald Jaeggi OSB) Jaeggi (* 3 January 1913 in Basel, † 25 April 1963) received his first music lessons from P. Otto Rippl. At the age of 14, he attended the Stiftsgymnasium in Einsiedeln, where he continued to receive musical encouragement and composed his first works. After entering the monastery in Einsiedeln, he took lessons in singing, choral conducting, harmony and counterpoint with Fr Otto Rehm. His ordination to the priesthood was followed by studies at the Pontifical Academy of Music in Rome in 1937. He interrupted his studies during the war and returned to Einsiedeln in 1940, where he first worked as a teacher at the Abbey School, before succeeding Fr Otto Rehm as Abbey Chapel Master of Einsiedeln from 1947 and becoming an active member of the Swiss Musicians’ Association.

In 1950, after working briefly in Hauterive, Jaeggi came to the Benedictine Abbey of Muri-Gries in Bolzano to support the ailing Abbey Kapellmeister Dr Anton Mayr. After his death in 1952, Oswald Jaeggi took over this position, the direction of the “Leonhard Lechner” choir, that of the Bolzano orchestra association and founded the “Leonhard Lechner” chamber choir according to Dr Mayr’s plans, which quickly enjoyed a high reputation far beyond the borders of South Tyrol and is still regarded today as a guarantee for the interpretation of choral music at a high artistic level.
From 1959, Oswald Jaeggi was represented on the Music Council of the ACV (Allgemeiner Cäcilien-Verband). A pulmonary embolism brought his work and artistic endeavours to an abrupt end; he died after a long illness in the cantonal hospital in Glarus, Switzerland.

Jaeggi’s compositions were performed at home and abroad, both at church services and at major international congresses. Many radio and disc recordings also bear witness to his first-class skills as a choirmaster.
His compositional output comprises almost exclusively sacred works, many of which were commissioned and often only completed a few hours before the première. He set 6 ordinaries, 17 propers, wrote around 150 motets, psalms, canticles, leading verses, songs and song movements, 23 organ works, several piano and instrumental works, as well as a number of secular compositions and song movements and several stage works, including the sacred opera “Thomas More”. His rather austere musical language is characterised above all by Gregorian chant, but is also very vocal and of great musical expressiveness.
In the last years of his life, he mainly wrote works in which the congregation was actively involved, both in German and in Latin, including his last ordinarium setting; the Missa “Trinae Unitatis” for congregational singing, monophonic choir and organ, which was completed within 9 days in January 1960.