AW: Midi Hammond

Robert Schrum Robert.Schrum at harpercollins.com
Fri Jul 24 16:57:00 CEST 1998


Most of the "features" that define the Hammond's sound are accidental, such as
key click or the mentioned velocity/pressure sentitivity.  The key click (that
Hammond tried to filter out only to hear complaints about the loss of
articulation) is merely contact noise impacting the relatively small signal
coming out of the generator coils.

I recently tried various keys on a well-worn studio B3 and my like-new X5 at
home.  When you depress a key slowly, there is no definite pattern to how the
nine harmonics come in on either organ.  When they do come in, the're really
grungy, as It's consistent for the same key, but not for the next.  It's
basically dependent on the amount of wear or bend that exists in each of the key
contact wires or buss bars.  I've never encountered pressure-sensitivity per-se
(a'la aftertouch) on a Hammond that was in condition worth playing.  The only
time you'd get this is if the keyboard wires or bars were really trashed.

The other thing that I have never even encountered in a MIDI hammond emulation
is the fact that Hammond keys bounce if released very quickly. (Remember Steve
Miller's "Fly Like an Eagle?")  Likewise, each successive bounce contacts fewer
harmonics.  You could bring this in on the upper end of release velocity values.

The switching device at each keying node would have to operate just like a
switch--either on or off (remember On-resistance must be sub-ohm!  DIP/reed
relays?)  If the devices switch on at a specific voltage threshold (like a
Schmitt trigger) just feed each one with slightly mismatched resistors with a
signal whose rising slope varies with note velocity.  Sum a little noise to add
contact bounce as the control voltages approaches and passes the thresholds, and
a 6-10Hz sine at release velocities above 100 or so.  Part count's getting
pretty $teep for a non-computer modeled solution, though (549 switches per
manual! :o )





-----Original Message-----
From: "Bill Layer" <b.layer at vikingelectronics.com> at hcinternet-server
Sent: Wednesday, July 22, 1998 12:55 PM
To: Haible Juergen <Juergen.Haible at nbgm.siemens.de> at HCINTERNET-SERVER
Cc: synth-diy at mailhost.bpa.nl at HCINTERNET-SERVER
Subject: RE: AW: Midi Hammond


At 12:30 PM 7/22/98 +0200, you wrote:
>
>       >The individual harmonics are
>       >not progressive as the note is pressed; they all contact at roughly
>the same
>       >time.
>
What?

>Hmm, I don't own a Hammond, but I used to own a Farfisa, which also
>had a lot of separate contacts under each key. And at least here,
>with this VIP 345, it made a great difference how fast you played
>the keys. Depressing a key slowly, one could clearly hear the harmonics
>come in one by one. While this is not exactly your standard playing
>style, it still demonstrates that you *can* phrase individual notes
>differently.

I must agree. I'm no Hammond expert, but I was under the impression (from
my Hammond-palying friends) that the ability to control note phrasing with
key pressure is a major feature of the Hammond tone wheel series. On my
humble M-3, I can very deliberately control the fullness of voice by
playing gently or firmly. This is especially apparent when using the
percussion voice.

My simple concept for controlling fullness with the MIDI 'initial key
pressure' message involves direct corrolation/quantization of the pressure
value to the number of harmonics to be included in the note. A hard
keypress would fold in all harmonics, while a moderate keypress would fold
in fewer harmonics, and a light touch might deliver only the fundamental etc..

Seems like it could work.


------------------------------
Bill Layer
Sales Technician

Viking Electronics, Inc.
1531 Industrial St.
Hudson, WI 54016

Phone: (715)386-8861 Ext. 210
Fax: (715)386-4344
E-mail: b.layer at vikingelectronics.com

http://www.vikingelectronics.com
24 Hour Fax Back System: (715)386-4345



More information about the Synth-diy mailing list