This demo, by retrosound, of the Roland VP330 Vocoder Plus, highlights the sound that Vangelis popularized in his soundtrack to Blade Runner and other works.
Richard Clews of SOS said this about the VP330:
If you ignore the hype and look at this instrument dispassionately, you’ll see it for what it really is — a 1970’s string machine with a built-in vocoder.
The vocoder itself is very nice, although not uniquely so, the strings are quite pleasant-sounding, if a little tinny, and as long as you make sure the ensemble effect is on, the human voice is excellent — a remarkable and unique sound. This is all very well, but the instrument is completely scuppered by its single envelope generator, which is shared by all of the notes you play. For many modern readers, the effect of this limitation, common to many ’70s instruments, may be difficult to imagine.
Suffice it to say that for anything other than monophonic lines or the simplest of chordal parts, the VP330 is horribly frustrating to play, and if you program a long release time, it’s just about impossible to come up with anything musical at all.