In the field of music and musicology, Hermann Kretzschmar, Max Friedlaender, Johannes Wolf, Curt Sachs, Georg Schünemann and Wilibald Gurlitt were among his teachers.
On 4 May 1928, he founded the Lübeck Singing and Playing Circle, which was influenced by the Jugendmusikbewegung [de], to spend their free time together doing sports, hiking and making music together.
In February 1931, Kühl, Distler and Grusnick introduced the then new service form of Musical Vespers in St. Jakobi, which soon became a firm tradition.
In addition to Distler's modernism, Grusnick's choir work focused on the Baroque composers Heinrich Schütz, Johann Sebastian Bach and soon Buxtehude.
He made his last trip to Uppsala in 1986 and published a printable copy of the Buxtehude cantata on "Nun danket alle Gott" before the end of 1990.