Midi Hammond

Larry Kirn lkirn at mich.com
Mon Jul 20 18:46:38 CEST 1998

Hi, Bill

I looked into this a long time ago, and ended up just synthesizing the output,
rather than continue with the tone generator.  The individual harmonics are
not progressive as the note is pressed; they all contact at roughly the same
time.  The reason for this crossbar switch is the fact that the drawbars serve
to route each of the nine individual keyboard busses to a single primary tap
of a current transformer, in order to control volume of that specific
harmonic.  Insertion impedance of as much as an ohm is significant, since
you're dealing with current (not voltage) outputs.  Even with a CPU to figure
out which harmonics went to which note (to avoid duplicate switches per
reluctance coil), there has to be a ton of switches.  When I originally looked
at this, low RDS FETs weren't cheap, but this seems viable if the transformer
were biased enough to keep them on during negative swings.  BTW, one thing to
watch out for that I didn't notice for a while is the fact that additional
uses of a harmonic (more keys pressed with it as a member) don't double its
volume, due to coil resistance.

I easily see your reason for wanting this - there's just nothing like a real


Bill Layer wrote:

> Is there any info on converting a Hammond tone generator organ to MIDI
> control?

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