They're each associated with a certain harmonic. The numbers themselves are based on how many feet long the pipes on a pipe organ had to be in order to generate the associated tone. (The Hammond organ was originally envisioned as an alternative to pipe organs.) The ones that are whole numbers represent ones that are octaves of each other. The ones that are fractional represent other harmonics.

[quotePost id=116151]They're each associated with a certain harmonic. The numbers themselves are based on how many feet long the pipes on a pipe organ had to be in order to generate the associated tone. (The Hammond organ was originally envisioned as an alternative to pipe organs.) The ones that are whole numbers represent ones that are octaves of each other. The ones that are fractional represent other harmonics.[/quotePost]

That's helps. Thanks!

Incidentally, Yamaha's first product was a reed organ in 1887.

Hi, i made this video about YC, you will find inside what are drawbar numbers and lot of other things:

There are others YC video on my Moessieurs You tube Channel , Organ History, Vibrato & Chorus, Rotary effect (release before OS 1.20), and updating OS 1.20.

Hope it's help.

And back in the "old days", music books intended for the Hammond organ had suggested registrations (draw bar settings) for each song. This is a composite of the cover and registration settings from an "old" Bach organ book (1956) and the registrations were printed on the inside of the cover (picture is sort of small because of the 2MB max limit on Yamahasynth.). The letters in circles or squares for "large models" were presets: the large models had one octave of reverse color keys on the far left of each manual and you pressed a note of that octave (circle was upper manual, square lower) to get the preset. And if you really wanted to make your own preset you could take a screwdriver and rewire the settings in the back of the instrument (I owned a B3 for 35 years or so)!