A talkbox creates a vocal effect which is often applied to a guitar. The musician uses the mouth to change / shape the frequency content of sound. They use a tube to do this whilst changing the shape of their mouth; this is mirrored in the frequency change in the original audio.
A vocoder analyses the vocal signal and applies it to a synth timbre. It sounds ‘robotic’ and the voice follows the pitch from the synth.
Other Creative FX
A ring modulator creates a dissonant effect that creates metallic and ringing sounds. It creates frequency products by adding and subtracting the input frequencies.
Overuse of pitch correction or autotune (a quick response time) forces the note to the nearest pitch set by the user / scale. It is often over-used in R&B music to create a slightly robotic effect, or subtly to keep vocalists in tune.
The term pan comes from ‘panorama’ in cinema. Auto-pan controls the place in the stereo field and is used to introduce creative panning throughout the stereo field. In tracks from the 60s and 70s, tracks were often extreme panned due to the limitations of technology.
A pitch shift alters frequencies and changes the musical note that is played. Harmonisers are intelligent pitch shifters that can add a musical interval to a part (e.g. a 3rd above). These effects would have been created historically by slowing down or speeding up a tape.