In addition to the dynamic tuning feature of Groven's organ, one can pre-select a fixed-set of pipes for the duration of a performance, a feature intended primarily for playing arrangements of traditional Norwegian folk music. While Norwegian folk music does employ non-tempered intervals, including what we might call 'blue-notes', it does not typically modulate, and thus does not require the automatic function. In total, there are from five to eight variants of each interval class available within Groven's system. There are, for example, seven different shades of minor thirds, including the just, Pythagorean, and 11:9 ratio minor thirds, although from any one particular pitch, there are, of course, only 3 different possible variants. With various fixed 12-note scales, Groven could come closer to approximating some of the distinct intervals found in Norwegian folk music, such as the so-called raised-4th and neutral-7th found in the nature-scale of the seljefløyte.
The seljefløyte is an indigenous folk instrument made from the branch of a willow. As there are no finger-holes, pitches are produced by over-blowing and stopping the end opening with your finger. The resulting scale, follows the intervals of the harmonic series and can be closely approximated on Groven's organ as shown in below.
In this realization, the 11th, 13th, and 7th partials deviate by a few cents up or down, while the other intervals are all within a half-cent from the indicated pure ratio. This is but one example of the numerous fixed-scales which Groven employed in his arrangements of Norwegian folk music.