tone switches – dolce, principale and strings, in 16', 8' and 4' footages. Later models include 16' bass, 8' flute, oboe, strings and 4' flute and strings. The first models have removable legs which could be stored inside the bottom cover, as opposed to later models that have folding or pivoting non-removable ones. The Compact Duo was introduced in 1966. It weighs and supports 49-key manuals. It features a four-octave upper keyboard with 9 selectors: 16' Bass, Strings; 8' Flute, Oboe, Trumpet, Strings; 4' Flute, Strings; 2-2/3' (Flute) and Brilliance, and a four-octave lower keyboard with three selectors: Dolce, Principale and Ottava. There are two inferior octaves on the left-hand side of the lower keyboard; one octave is switch-controllable for choice of a bass or acute sound. The instrument has four vibrato and three reverb settings. Later models also incorporate tremolo, percussion and repeat functions for both the upper and lower treble manuals independently. Unlike other Compact series organs, the Compact Duo models require a separate power supply/solid-state preamp/real spring reverb unit (called the Farfisa F/AR), to which the organ connects via a multi-lead cable. Alternatively, it can be powered by a separate Farfisa TR/60 amplifier. Farfisa updated the Compact range through the 1960s, adding new features, but without changing the general model name. Later Compact models, such as the Combo Compact I introduced in 1968, include two inferior octaves (one black/white, one grey/white) on the left hand side of the keyboard. One set of octaves is switch-controllable for choice of a bass or acute sound with bass note sustain and controllable bass percussion. The volume balance between bass and treble is adjustable. The Compact Deluxe features similar controls to the Compact I, with additional voices such as the 2-2/3' footage with an independent "brilliant" tab. Later models, such as the Combo Deluxe Compact I, also include a rhythm section (drum machine) of brush cymbal and drum. The final Compact models were manufactured in 1969. The Compact series has caused reliability problems for later collectors. It features germanium transistors which tend to drift in value, and the plastic keys have tended to degrade over time, leaving cracks. Other problems include corroded contacts, leading to non-working switchings, and failing electrolytic capacitors. The design of the instrument makes it difficult to access components and service them. FAST Series (1967–1971) The FAST (Farfisa All Silicon Transistor) Series models were first introduced in 1967,