Vocoders and Talkboxes are often confused in that both sound like synthetic voices and are often created using synths; they also require pretty much zero singing ability to use, which is great if you want to add lyrics to your track without being able to hold a tune. However, that’s where the similarity ends.
I’m going to explain the difference between the two and demonstrate how you can get both of them working in Ableton and Logic.
The vocoder (a portmanteau for voice encoder) has been around since the 1930s, though the sound is synonymous with music from the 70s and 80s onwards.
A subtle but well-known example is the intro to Kraftwerk’s 1974 single, Autobahn. It can be heard around 13 seconds in:
In principle we have two signals: a carrier and a modulator. The carrier’s signal is divided into frequency bands, and the amplitude (volume) of each band is modulated by the corresponding band in the modulator signal.
The Roland SVC-350, image © SoundToys
Most commonly this is heard with a synthesiser as a carrier and a voice as the modulator, in effect making the synth ‘talk’ and mapping the harmonic characteristics to the voice. This is one of the most common uses for vocoding, and can be more clearly heard in Giorgio Moroder’s E=MC² (1979), Devo’s Beautiful World (1981) and Kleeer’s Tonight (1984).
The Science Bit
Let’s take a brief look at what’s happening under the hood. The carrier signal is analyzed by the vocoder and divided into a number of bands using a band-pass filter. A band-pass filter isolates a frequency ㅡ you can imagine it like a high-pass filter and a low-pass filter stuck together.
A Band-pass filter at 500 Hz.
The number of bands is normally somewhere between 6 and 20. Older vocoders typically had fewer bands while while modern ones can have up to 32, and are therefore more detailed.
You can imagine a vocoder to be a little bit like a Graphic Equaliser but instead of manually amplifying or attenuating each band, it’s actually controlled by the corresponding band in the modulator signal. This is how the characteristics of the modulator are translated to the carrier’s timbre.
SoundOnSound has created this handy diagram demonstrating a 10-band vocoder. The amplitude of the modulator signal generates an envelope which is mapped to the same band in the carrier signal. Envelopes create rises and falls in voltage that can control parameters such as amplitude, pitch and filter cutoff frequency etc. In this instance, they control a VCA (voltage controlled amplifier) of the band. In essence, the amplitude of a band present in the modulator controls the amplitude of the same band in the carrier.
Image © SoundOnSound
How many bands the vocoder has generally determines the quality of the modulator’s signal. Some Vocoders work as an insert effect, needing a carrier to be fed into them, while others are built into a synthesizer that provides that side already. Still others can be synthesizers with the option to take an external line input for the carrier.
Here are some other tracks that famously use vocoding.
Afrika Bambaataa & Soul Sonic Force – Planet Rock 
Beastie Boys – Intergalactic 
Daft Punk – Harder Better Faster