Until 1975, sound was created by an electric current from rotating a metal tonewheel near an electromagnetic pickup, and then strengthening the signal with an amplifier to drive a speaker cabinet.

[9] Hammond organ manuals and pedalboards were originally manufactured with solid palladium alloy wire to ensure a high-quality electrical connection when pressing a key.

[33] Hammond was inspired to create the tonewheel or "phonic wheel" by listening to the moving gears of his electric clocks and the tones produced by them.

[36] He gathered pieces from a second-hand piano he had purchased for $15 and combined it with a tonewheel generator in a similar form to the telharmonium, albeit much shorter and more compact.

Since Hammond was not a musician, he asked the company's assistant treasurer, W. L. Lahey, who was also a trained organist, to help him achieve the desired organ sound.

[41] For all its subsequent success with professional musicians, the original company did not target its products at that market, principally because Hammond did not think there would be a sufficient return.

[43] The complaint resulted in lengthy hearing proceedings, which featured a series of auditory tests that pitted a Hammond costing about $2600 against a $75,000 Skinner pipe organ in the University of Chicago's Rockefeller Chapel.

[44] During the auditory tests, sustained tones and excerpts from musical works were played on the electric and pipe organs while a group of musicians and laymen attempted to distinguish between the instruments.

[45] In 1938, the FTC ordered Hammond to "cease and desist" a number of advertising claims, including that its instrument was equivalent to a $10,000 pipe organ.

[4] To address concerns that the sound of the Hammond was not rich enough to accurately mimic a pipe organ, the model BC was introduced in December 1936.

[29] To cater more specifically to the church market, Hammond introduced the Concert Model E in July 1937, which included a full 32-note pedalboard and four electric switches known as toe pistons, allowing various sounds to be selected by the feet.

[9] The E-100 series was a cost-reduced version of the A-100 introduced in 1965, with only one set of drawbars per manual, a reduced number of presets, and a slightly different tone generator.

"[64] Though the instrument had been originally designed for use in a church, Hammond realized that the amateur home market was a far more lucrative business, and started manufacturing spinet organs in the late 1940s.

[74] The company had stopped manufacturing tonewheel organs entirely by 1975, due to increased financial inefficiency, and switched to making IC models full-time.

[100] The Leslie was originally designed to mimic the complex tones and constantly shifting sources of sound emanating from a large group of ranks in a pipe organ.

[85] As well as faithful reissues of the original 122 speaker, the company announced in 2013 that they would start manufacturing a standalone Leslie simulator in a stomp box.

[111] Crosstalk or "leakage" occurs when the instrument's magnetic pickups receive the signal from rotating metal tonewheels other than those selected by the organist.

[112] However, the sound of tonewheel crosstalk is now considered part of the signature of the Hammond organ, to the extent that modern digital clones explicitly emulate it.

Third-party companies manufacture adapters that can allow a Hammond organ designed for one region to run in the other, which are used by internationally touring bands.

[120] Clavia introduced the Nord Electro in 2001; this used buttons to emulate the physical action of pulling or pushing a drawbar, with an LED graph indicating its current state.

"[137] Fisher played the organ lines on Procol Harum's "A Whiter Shade of Pale", which topped the UK charts in the summer of 1967.

[138][139] Steve Winwood started his musical career with the Spencer Davis Group playing guitar and piano, but he switched to Hammond when he hired one to record "Gimme Some Lovin'".

[140] Gregg Allman became interested in the Hammond after Mike Finnigan had introduced him to Jimmy Smith's music, and started to write material with it.

[144] Deep Purple's Jon Lord became inspired to play the Hammond after hearing Jimmy Smith's "Walk on the Wild Side".

[148] Van der Graaf Generator's Hugh Banton modified his Hammond E-100 extensively with customized electronics, including the ability to put effects such as distortion on one manual but not the other, and rewiring the motor.

Author Edward Macan thinks this is because of its versatility, allowing both chords and lead lines to be played, and a choice between quiet and clean, and what Emerson described as a "tacky, aggressive, almost distorted, angry sound".

[150] Emerson first found commercial success with the Nice, with whom he used and abused an L-100, putting knives in the instrument, setting fire to it, playing it upside down, or riding it across stage in the manner of a horse.

[151] Other prominent Hammond organists in progressive rock include Argent's Rod Argent, Yes's Tony Kaye and Rick Wakeman, Focus's Thijs van Leer, Uriah Heep's Ken Hensley, Pink Floyd's Richard Wright, Kansas's Steve Walsh, Mott the Hoople's Verden Allen, and Genesis's Tony Banks.

[153] Winston Wright was regarded in the music scene of Jamaica as one of the best organ players, and used the Hammond when performing live with Toots and the Maytals, as well as playing it on sessions with Lee "Scratch" Perry, Jimmy Cliff, and Gregory Isaacs.

[154] Tyrone Downie, best known as Bob Marley and the Wailers' keyboard player, made prominent use of the Hammond on "No Woman, No Cry", as recorded at the Lyceum Theatre, London, for the album Live!