"8:30" was the first recording on which Zawinul used a vocoder. Asked about it in 1984, he said, "I've done a lot of things with [the vocoder] over the years. The whole melody on '8:30' was a vocoder melody. And, for instance, on 'Procession' the didgeridoo-type sound is all done with the vocoder, as well as the 'chipmunk' voices on 'Two Lines.'" The vocoder he used was the newly introduced Korg VC-10, a standalone device that included a small keyboard, a simple synthesizer, and a goose-neck microphone attachment. The idea was to impart the timbral character and articulation of speech onto a synthesized sound generated by the VC-10 itself or from an external sound source. (According to Zawinul keyboard technician Jim Swanson, Zawinul generally used the synthesizer in the VC-10 as opposed to an external synthesizer.) If you used a bass sound as the audio source, for instance, then the vocoder made the bass "talk." The VC-10 was part of Zawinul's live set-up at least through 1984, when he actually had two VC-10s, one of which was modified by Swanson by detaching its keyboard so that it could be placed on top of one of Zawinul's keyboard stacks. He eventually replaced the VC-10s with a Korg DVP-1 voice processor, which was introduced to the market in 1986 and was still a part of Zawinul's set-up as of 1997.