Mielck composed all his works in the short span of four years. His catalogue includes a large number of works in the field of chamber music, including a string quintet and a string quartet. He also composed a symphony (1897), two overtures, a concert piece for piano and orchestra as well as one for violin and orchestra, the Finnish Suite, and two major vocal works in the German language.

Mielck faced disappointment in his home country for the lack—with the exception of the Finnish Suite—of nationalistic (political) tendencies; his interest in the culture of his ancestral Germany made him rather a foreigner in the Finnish music scene.

It was in Germany, shortly before his death, that Mielck found his greatest success.

The enthusiasm aroused in the critics—mainly in Karl Flodin at the “Nya Pressen” — by the premiere of Mielck’s symphony, in October 20, 1897, conducted by Robert Kajanus, was a motivation that prompted Sibelius to try his hand at his first symphony.