Shown is an edit screen from the JD-990. This is the "structure" page, which determines how the processing blocks are to be organized in a given patch. The ability to do this is one of the improvements that the JD-990 has over the JD-800; the JD-800's processing architecture is fixed in the configuration shown on the left side. On the right side, we see a ring-modulation type patch. Tone C goes through a TVA (equivalent to a VCA), and then is multiplied by tone D. (The "R" in the box represents ring modulation, which is implemented in the digital realm by simple multiplication of the individual samples from each input. Ring modulation is one of the few synth functions that is difficult to do well in analog circuitry, but trivially easy to do in digital synthesis.) The patch then passes through two TVFs (equivalent to VCFs), and a final TVA to shape the output.
One of the nifty things about the JD-990 is that you can use a JD-800 to edit patch parameters on the 990. Every parameter slider on the 800 will edit the corresponding parameter on the 990, once you've done all of the needed MIDI setup. Both of the synths should be set to the same unit number. Rx of sysex has to be enabled on the 990; press SYSTEM SETUP and then Rx MIDI (F4); the parameter is on the bottom right. (Actually, if you set it to ON-1, the unit numbers don't have to match; it will receive sysex from any unit number. But note that this can cause chaos if you have two or more 990s in your setup.) On the 800, you need to set it to transmit sysex for patch editing. Press MIDI, and then use the PAGE up/down buttons until you get to "Tx Edit Data". Use the slider or press INC/YES to set it to "ON". Unfortunately, the 800 doesn't remember this settting across power cycles, so you will have to do it again each time. It's also a good idea, while in the MIDI menu, to page to "Local control" and set it to "OFF", so that you won't get confused if you hear both the 800's and the 990's audio. (Note that setting local control OFF does not stop the sliders from editing patches on the 800. So make sure you don't hit WRITE on the 800 if you are intending to edit the 990!
The 800's patch editing controls will edit the corresponding parameters on the 990 (and the 990's screen will update in real time if you happen to be looking at the screen where that parameter is), but remember that the 990 has parameters that the 800 doesn't have. You have to edit these parameters on the 990's screen. The first time I tried to use the pitch envelope in a 990 patch, I was baffled because none of the pitch envelope sliders on the 800 was having any effect. Turns out that the 990 has a pitch envelope amount parameter (called "Pitch Env Depth"; press WG then Pitch) that the 800 doesn't have, and it was set to 0, causing the pitch envelope to be ignored. On the 800, if you don't want the pitch envelope to do anything, you have to set all the level sliders to 0.
One other thing you have to be careful about is understanding how the individual tones are addressed. The 990 has a row of tone select buttons that determine which tone you are looking at when you are editing on the 990's screen. But understand this: each parameter in each tone has its own sysex address. (In other words, the TVF resonance in tone A has a different sysex address than the TVF resonance in tone B.) When you are using the 800 to edit the 990, the sysex addresses that are sent are determined by which tones are selective as Active (flashing lights) on the 800. This means that if you have tone D selected in the Tone Select buttons on the 990, but tones A and B are Active on the 800, when you move a slider, it will edit tones A and B on the 990! I've found that it's a good idea to only edit one tone at a time and always keep the same tones selected/active in both places; that reduces confusion when going back and forth between the 800's sliders and the 990's screen when editing. (Just to make things more confusing, the LAYER selection on the 800 does not send any sysex, and so it will not change the on/off status of the tones on the 990. You have to change that using TONE SWITCH buttons on the 990.)
A few other things:
- The 800 must be in SINGLE mode for this to work; if it is in MULTI mode it will not send the right sysex strings.
- Yes, the Palette sliders work to edit the 990. In fact, you can do the same trick you can do on the 800, where you have no Tones active and then you move a slider, editing nothing but making that parameter the current parameter for the Palette.
- Keep in mind what structure you have selected on the 990 when editing from the 800. The 800 doesn't know about structures; you may think that you are editing only tone A's VCF, but if you have selected a different structure, it may effect both tones A and B, for instance.
- Remember that even an un-expanded 990 has waveforms that the 800 doesn't have. You cannot access all of the waveforms using the 800's waveform selection knob. If you want to select a waveform numbered higher than 128, you'll have to go to the 990's screen. You'll also have to do this if you want to select a waveform from an expansion board.
- The 990's LFOs also have a few extra waveforms that can't be selected from the 800.
- You cannot edit the 990's effects parameters from the 800.