Roland AT900 Music Atelier Owner's Manual page 57

Time
8' volume: 8
Time
4' volume: 5
What's the feet?
"Feet" is a term that began as a measurement of the length of the pipes in a pipe organ.
The pipes that produce the basic pitch (fundamental) for each note are considered to be "8 feet" in length.
Therefore, a pipe producing a pitch one octave below that of the reference of 8' (eight feet) would be
16'; for one octave above the reference, the pipe would be 4', and to take the pitch up yet another
octave it would be shortened to 2'.
The pitches of the harmonic bars are related as follows.
When the middle C (C4) note is pressed, each
harmonic bar will sound the following notes.
16' 5 1 / ' 8'
3
one octave 5th root
below
8' =
On tonewheel organs, the high-pitched footage for a portion of the high range, and the low-pitched
footage for a portion of the low range are "folded-back" in units of one octave.
Folding back the high-frequency portion prevents the high-frequency sounds from being unpleasantly
shrill, and folding back the low-frequency portion prevents the sound from becoming "muddy."
On the ATELIER faithfully simulates this characteristic.
Time
4' 2 2 / ' 2' 1 3 / '
3 5
15th
8th 12th 17th
Selecting and Playing Sounds
1 1 / ' 1'
3
19th 22nd
55