Roland V-Combo VR-760 Owner's Manual page 34

Performing with the Keyboard
The numbers (16', 5-1/3', etc.) printed on the knob of each harmonic bar
indicate the pitch of that bar in "feet." The pitch of each harmonic bar plays
an important role in creating the tone. The 8' pitch is the basic pitch of the
sound, and the sound is created based on this 8' pitch.
The pitches of the harmonic bars are related as follows.
fig.04-10(relationsOfHarmonicBar)
When the middle C (C4) note is pressed, each
harmonic bar will sound the following notes.
16' 5 1
one octave 5th
below
34
/ ' 8' 4' 2 2 / '
3 3
root 8th 12th
8' =
2' 1 3 / ' 1 1 / ' 1'
5 3
15th
17th 19th 22nd