Rieger Orgelbau is an Austrian organ-building company tracing its origins back to 1845 when Franz Rieger founded the firm in Jägerndorf (Austrian Silesia). After the expulsion of its owners from Czechoslovakia in 1946, the company relocated to Schwarzach in Vorarlberg. At the old factory in Krnov (formerly Jägerndorf), the Czechoslovak company Rieger-Kloss was established, which also built organs until it ceased operations in 2015.

Initially, Rieger built typically German Romantic organs, although few original specifications have been preserved, making it difficult to fully characterize Rieger's early style. Many of these organs were later altered and are therefore not in their original state. At the beginning of the 19th century, Rieger's organs featured relatively few 8′ stops, generously staffed the swell divisions with numerous reeds, contrary to the German Romantic style.

After World War II, the newly established company in Schwarzach operated under severe financial constraints and couldn't afford to develop its own style. Consequently, it followed the trends of German firms and produced many neo-baroque instruments. However, as early as 1965, Rieger began incorporating romantic undulations in the swell divisions, a practice that gradually increased, although the number of 8′ stops in other divisions remained small. In the 1970s, as interest in French organs grew, Rieger quickly adapted by adding more 8′ stops and robust French Bombarde stops in the pedal division, even in smaller organs, instead of the usual Posaune stops.

The use of 8′ stops has remained relatively low, with more than four typically found only in the swell division. The company's style changed again when Eberle took over, reducing the frequency of Bombarde stops and the number of 8′ stops compared to those commonly built by Christoph Glatter-Götz.

https://de.wikipedia.org/wiki/Rieger_Orgelbau
https://www.rieger-orgelbau.com/de