A Mixture stop in which the ranks increase in number as the notes progress from bass to treble. It was invented by Musikdirektor F. Wilke of Neu-Ruppin, Germany as a means of reinforcing the treble. The original Progressio Harmonica started with two ranks, 1-1/3' and 1', and added a third 2' rank at tenor C. Other treble-reinforcing stops include Diskantprinzipal.

Progressio Harmonica II-IV, Brustwerk; Cathedral of Merseburg, Saxony, Germany; Ladegast 1853-55. Progressio Harmonica II-IV, 3rd Manual; Cathedral of Schwerin; Ladegast.

Progressio Harmonica II-V, 2nd Manual; Smetana Hall, Prague, Czechoslovakia; Voit/Tucek 1912. (Changed to III-VI by Vleugels in 1997.) Progressio Harmonica III-V 2-2/3', Schwellwerk; Konzerhaus, Vienna, Austria; Reiger 1913.

Progressio III, 3rd manual; Festhalle, Koblenz, Germany; Voit 1902 (destroyed). Progressio III-V 2-2/3', manual; Fernorgel, Cathedral, Passau, Bavaria, Germany; Steinmeyer 1924.

Progressio IV-VI 2-2/3', Schwellwerk; Dom, Fulda, Germany; Sauer 1875-77. (Modified by various builders.)