text: (1950–) Shortly after the debut of the spinet, the chord organ appeared. This is an even simpler instrument designed for those who wanted to produce an organ sound in the home without having to learn much organ (or even piano) playing technique. The typical chord organ has only a single manual that is usually an octave shorter than its already-abbreviated spinet counterpart. It also possesses scaled-down registration and no pedalboard. The left hand operates not a keyboard but an array of chord buttons adapted from those of an accordion.
  The original Hammond Chord Organs in 1950 are electronic instruments using vacuum-tube technology. In 1958 Magnus Organ Corporation introduced chord organs similar to an electrically blown reed organ or harmonium.
  (1957–)
  Electronic organs before the mid-1950s had used vacuum tubes which tended to be bulky and unstable. This restricted attempts to extend features and spread their use into homes. Transistors, invented at Bell Labs in 1947, went into practical production in the 1950s, and their small size and stability led to major changes in the production of electronics equipment, in what has been termed the "transistor revolution".
  In 1957, a home organ manufacturer, Gulbransen, introduced the world's first transistor organ, Model B (Model 1100). Although it uses transistors for tone generation, vacuum tubes are still used for amplification.
  And in 1958, Rodgers built the first fully solid-state transistorized organ for church, called Opus 1 (Model 38). Other manufacturers followed.