Following the war, the Czechoslovak government expelled the Ethnic German owners and workers of the original firm from Czechoslovakia, and nationalised the Rieger company.

Rieger–Kloss met with success at the World Exhibition Expo 58, which led to 46 commissions in republics of the Soviet Union.

They have built over 600 organs using pneumatic, electro-pneumatic and tracker action, and made a large number of restorations of historic instruments.

They take in twelve students from all over Europe each year, who pursue a four-year course of intensive study culminating in difficult written and practical exams.

Subjects they cover include the English, German, French, and Czech languages, mathematics, organ playing, organ history, physics, mechanics, pipe and action building, acoustics, electrical engineering, technology, quality of materials, technical drawing, economics, and gymnastics.