JP-8080 Voice Modulator Explained
The section in question is called the Voice Modulator. The JP-8080's manual explains it rather poorly due lumping the three distinct functions of the Voice Modulator into a few pages. It would have been much easier to understand if they had broken it up and that's what I'm going to try to do and explain each portion separately.
The 3 sections of the Voice Modulator are the filter bank, vocoder and vocal morph control. Part of what makes it hard to understand is that Roland made many of the settings not automatic and leaving many of the settings manually controlled. This is very nice but make it that much harder to understand. Many of the different component of the Voice Modulator integrate into many of all 3 functions of the Voice Modulator. Fist, the Voice Modulator On button. All this does is turn on the 'little black box' of the Voice Modulator. Few people actually know what actually goes on in there and even pg. 104 just shows it as the 'box'. To activate the different functions of the Voice Modulator usually takes more than one setting change (which adds to the complexity).
Vocal Morph Control. This is rather simple, yet a very fun and powerful feature of the 8080. THE Vocal Morph Control simply analyzes the incoming Vocal/Upper input relative to the spoken 'a' (1.2 kHz) and translates it to midi CC messages. Exactly what midi messages it is assigned to is specified on the top of page 104 and page 84. Think of it as a 'breath controller', but instead of translating breath, it translates sound. This is set independently of any other setting in the Vocal Morph Control section. You do not have to use the Filterbank or the Vocoder to use the Vocal Morph Control. As far as I know it is the only one of it's kind in a mass marketed product.
Filter bank and vocoder. These two are almost setup identical. The one setting that determines which mode you are in is the algorithm. The vocoder needs two signals (carrier and modulator) while the filter bank only needs one, but can use more.
Filter bank. If the algorithm (EDIT + Bank 2) is FLT BANK WIDE or FLT BANK NARROW then the Voice Modulator is automatically is filter bank mode. It is just a 12 band filter of what ever sound you feen the input of the Voice Modulator. You can send internal synth sounds by using Vocal Mod Send or external signals by feeding the external input. Here's how to setup the filter bank.
Vocoder. If the Algorithm (EDIT + Bank 2) is WIDE, SMOOTH or SOLID, then the Voice Modulator is in automatically in Vocoder mode (usually referred to as Formant Filter in the manual). You can use internal or external sound for the carrier (sound to be modified, typically synth pad sound), while you have to use external sound for the modulator (tpyically your voice). There are audio path settings to determine which sound you are going to use. Here's how to setup the vocoder.
Traditional filter method. While not related to the Voice Modulator, I'd though to include this to show how this is setup. This is more in the traditional style of EXT INPUT used on other synths such as SuperBassStation, Waldorf Q/MWXT and Access Virus. This explanation is here.