Planetone shares plans to build the Morphatron, a big ol’ analog vocoder and formidable soldering project –
I designed it from scratch, although I did investigate as many vocoder schematics I could get my hands on. I focused on using easily obtainable components that are inexpensive, and I tried to keep the circuit as simple as possible without sacrificing functionality.
A vocoder basically has two inputs and one output. The first input is the program (usually a connected to a microphone) and the second input receives a carrier signal (usually a keyboard). The program signal is then fed to an analysis section, which extracts the spectral information from the sound and applies it to the carrier signal. This vocoder will analise the signal on 14 bands, but the design can easily be modified to include more channels, or actually fewer (if you are in a hurry).
Though not exactly a beginner’s project, much of the assembly involves building multiples of the same board – making the whole seem a bit less daunting. Schematic, steps, and demo available on the project’s instructable.