A Low Frequency Oscillator. It is similar to a normal oscillator except that it outputs very low frequencies (very slow waves) and is used as a control input into another part of the synth. Examples of its use are to create vibrato or tremolo effects....
Synthi 100
"In 1974, EMS introduced the Synthi 100, designed for those who didn't need a portable
system. As [designer, Dave] Cockerell put it, 'You had to take walls down to get it into
studios.' The Synthi 100 was originally based on three VCS3s, and grew from there to
encompass 12 oscillators and associated filters, envelopes, etc. It also had a three-track
monophonic digital sequencer and two 64X64 patch matrices. The Synthi 100 sold for
around £10,000 (US $25,000), which limited the number of units sold, but it was the
only thing Britain ever produced that could compete with the modular systems from
American manufacturers. One Synthi 100 went to the BBC Radiophonic Workshop,
which does electronic music and sound effects for a myriad of TV programs, including
Doctor Who.