Notice the large round ferrite tuning cores of the transistor oscillators. Tone generation is another category. Older Hammond organs use a mechanical system to produce tones called tonewheel generators. These organs truly never need tuning . Oscillators are electronic circuits that continually switch states to produce repetitive output signals.
Frequency is synonymous with pitch .
The waveform of the output determines the tone or timbre of the sound. Voicing circuits modify the basic waveform for a variety of sounds. For instance, a sinewave produces a flute sound and a squarewave produces a reed sound. Several different waveforms can be modified and blended, and even distorted, to produce a unique sound. Digital sampling has produced some fairly authentic pipe organ sounds.