A type of electronic organ which was popular with rock and pop groups in the 1960s. Combo organs were designed to provide a light and portable alternative to large, heavy console organs; they were typically encased in plastic cases and supported on lightweight aluminum stands. Unlike the Hammond organ, combo organs were entirely electronic, and nearly all were entirely solid state. As such, they were among the first electronic instruments to use no tubes (valves).
A typical combo organ relied on top octave division to produce a basic waveform which was filtered in various combinations to produce organ-like sounds. On most models, the possible combinations of available sounds was fairly limited. Some had simple vibrato or tremolo circuits to provide some variation. A few models include a provision to connect a set of bass pedals, and some had a provision for the keyboard to be split, with the lowest one or two octaves switchable to a bass sound. Usually, such models would visually indicate the bass octaves using reverse keys, although some models had the entire keyboard done in reverse keys. A few deluxe models had dual manuals.
Among the manufacturers of the best-known combo organ models were Vox (whose Continental model is regarded as the archetype of the genre), Farfisa, Hohner, and Gibson. The first models appeared around 1961 and manufacturing of most ceased in the early 1970s, as combo organs fell out of popularity. The sound of combo organs is often described as rather shrill, although this depends on the model and the combination of sounds used; the use of top-octave division could result in a static sound that fatigued the ear unless effects were used. Many players switched to Hammond or similar organs as the cost of these declined after 1970, and they provided more sonic versatility. Combo organ models that were once popular are now regarded as collectable.