The instrument
The last tone-wheel organ was the T-500-series. It is almost identical to the T-100 - T-400 organs, but as with any revision of the circuitry. The chorus/vibrato was now individually selectable for upper and lower manual. Hammond also integrated the Rythm III unit and added an internal Leslie and Leslie 700-series socket.
The T-522 has 2 manuals with 44 keys for 3 1/2 octaves. The upper manual has 9 drawbars 16', 5' 1/3, 8', 4', 2' 2/3, 2' ,1' 3/5 ,1' 2/3,. 1', the presets String 8', Full Tibias 16' and Theatre Brass 16', the percussion presets Glockenspiel, Celesta, Guitar, Marimba, Xylophone and Banjo with Repeat, as well as controls for the repetition speed Vibrato/Celeste, Vibrato Small, Vibrato/Chorus and Upper. For the lower manual there are 7 drawbars 8', 4', 2' 2/3, 2', 1' 3/5, 1' 1/3, 1', Ensemble 8', the bass pedal drawbars 16', 8'. Reverb I and II are also available.
Details
Electrical impulses of various frequencies are produced within a tone generator, containing a number of tone wheels driven at predetermined speeds by a synchronous motor and gear arrangement. Each phonic wheel is similar to a gear, with high and low teeth. As the wheel rotates these teeth pass near a permanent magnet, and the resulting variations in the magnetic field induce a voltage in a coil wound on the magnet. This small voltage, when suitably filtered, produces one note of the musical scale, its pitch or frequency depending on the number of teeth passing the magnet each second. A note of the organ, played on either manual or the pedal keyboard, generally consists of a fundamental pitch and a number of harmonics of the fundamental frequency. The notes available on each key are individually controllable by means of drawbars and preset keys.
The signals passes through the expression control and through the preamplifier, where vibrato is introduced, to the power amplifier and the self-contained speakers. Reverberation is added electrically by a second amplifier which drives a reverberation speaker, also located in the console.