Clonewheel organ

The Hammond organ's individual waveforms were made by mechanical tonewheels which rotated beneath electromagnetic pickups.

Originally, key click was considered to be a design defect and Hammond worked to eliminate or at least reduce it by using equalization filters.

However, some performers liked the percussive effect, and it has become part of the classic sound that modern imitators of the Hammond organ have tried to reproduce.

As well, the Hammond, as with all vintage electromechanical instruments, faces the risk of technical problems with the tonewheels or electric motor, which may be difficult to resolve in a touring situation.

Some early emulation devices from the 1970s were criticized for their unrealistic imitation of the Hammond sound, particularly in the way the upper harmonics were voiced, and in the simulation of the rotary Leslie speaker effect.

By the 1990s and 2000s digital signal processing and sampling technologies allowed for better imitation of the original Hammond sound, and a variety of electronic organs, emulator devices, and synthesizers provided an accurate reproduction of the Hammond tone, such as the Kurzweil K2600 and Clavia Nord Electro keyboard.

Some sophisticated emulation devices have algorithms that recreate many of the nuances of vintage Hammonds, such as the "crosstalk" or "leakage" between tonewheels, the sound of dirty key contacts, key click, a growling tube amplifier, and digital simulations of the rotating Leslie speaker cabinet.

In between are numerous keyboard-based models from Hammond, Korg, Roland, Clavia (Nord Series), rack-mounted modules, and software-based "virtual synths" (such as the B4 by Native Instruments) which provide simulations of the B-3 sound.

The argument that digital simulations cannot recreate the complex interplay of variables that create the "Hammond sound" (tonewheel leakage, Leslie speaker rotation, etc.)

The Hammond XB-2 recreates the sound of the vintage electromechanical Hammond organs in a much lighter, smaller keyboard that uses electronic circuits to reproduce the sound of the spinning tonewheels.
Typical tonewheel organ and rotating speaker (Hammond B3 & Leslie).
Korg CX-3 (1980)
According to journalist Gordon Reid, it "came close to emulating the true depth and passion of a vintage Hammond." [ 1 ]
The NordElectro2 reproduces the sound of the Hammond organ and several other electromechanical instruments. Unlike most "clonewheel" instruments, the Nord does not have sliding drawbars. Instead, the player presses buttons which light up a row of LEDs to indicate the drawbar setting.
Roland VK-7 (1997)
Even though the VK-7 recreates the Hammond sound using electronic circuits, the instrument gives a nod to the traditional heritage of the Hammond by using a wooden case.
A WERSI OX7 organ sound module, which includes drawbars.
Vox Continental (1962–early 1970s)
Hammond X5 (c.1974/1975)
Elka X-50 clonewheel organ (1982)
Korg BX-3 (1980)
Hammond XB-3 (1994)
Clavia Nord C2D Combo Organ (2012–)
KeyB Duo