Modern derivatives of Dudley's vocoder are widely used in speech coding, for example for transmission of speech over the internet and for digital cellular telephones. The basic technique has also been adapted by musicians for special effects. The following demonstration is taken from a film by Laurie Anderson called "Home of the Brave," on a track called "Sharkey's Night." Both singing voices you hear are Anderson's, but one is pitch shifted using a vocoder.
Note that the audio file is a huge file (16,448k), in Sun audio format, CD quality (44.1kHz sampling, 16-bit samples). Not all players will be able to handle it. In particular, note that most of Sun's own software will not handle it (the AF program, for example). To play it on a Sun workstation that can handle CD formats (an ultrasparc), download the file to disk, then use "audiotool" to play it.