Dupla

Dupla (Lat.: double), a now obs. prefix to names of organ stops; as such, dupla meant double the size, or an oct. lower, e.g., dupla sesquialtera, which is an oct. lower than sesquialtera. The Engl. and Fr. equivalents are “double” and “double” (133). Mahrenholz, Christian. Die Orgelregister, ihre Geschichte und ihr Bau. Kassel, 1942.