Two-Keyboard MIDI Setup, In General
I've just recently gotten a second keyboard and have put some thought into how to get the MIDI setup I want. Since someone else was asking me about it, I'll describe the setup in general and then specifically for one or two types of keyboards. The idea is to have a good MIDI setup for live playing with two keyboards that can be extended to use other MIDI-controlled gear as well.
The setup looks like this: both keyboards are connected via MIDI, and both are listening to different channels. One keyboard, which I'll call the master, has all the presets you need for a gig in order. When you pick a new preset on the master, it should send a *specific* program change to the other keyboard (which could be the same preset number as the one you've switched to on the master, but you're more limited that way). If your master keyboard allows it, you can use a footswitch to step through the program changes in order and have the other MIDI devices change programs accordingly. What you want to definitely avoid is having to change programs on more than one MIDI device and having to do it with mroe than one press of a button. You'll also want to be able to play on either or both keyboards and have either or both keyboards produce the sounds.
Firstly, you need to pick one of the keyboards to be the master. This *doesn't* have to be the better keyboard to play on (in my setup, it's the opposite); the master keyboard should be the one that is best at controlling other MIDI devices. Ideally, you want your master to be able to send program changes to all the other devices.
Next, MIDI connections. With two keyboards, connect the MIDI IN with each keyboard to the MIDI OUT of the opposite keyboard. If you have another MIDI-controlled devices (I use a Line6 PodXT guitar effects unit), hopefully one of the two devices other than the master has MIDI THRU, since that will be faster than a MIDI OUT A -> MIDI IN B -> MIDI OUT B -> MIDI IN C chain.
Next, MIDI channels. Each keyboard should be set to listen to data on different channel, or possibly multiple different channels depending on how well each keyboard does layers and splits. This may be done by setting a global MIDI channel, by setting MIDI channels in individual combinations/programs, or both.
What MIDI control data do you want to send to each keyboard? Obviously, knobs that send MIDI CC events on one keyboard may send them to another, and you don't want to tweak your synth pad and find out that you've also applied distortion to the piano sound playing on your other keyboard. In general, you don't want to send MIDI CC events at all, but there are exceptions.
One is pedals. You can't use more than two pedals at the same time, and most people aren't used to using a sustain pedal with their left foot, so you probably want to set it up so that one keyboard has the sustain pedal plugged into it but also sends the appropriate CC messages to the other keyboard. You might want this with an expression pedal as well.
The other exception is the pitch bend and mod wheels (or their equivalents, like the joystick found on most Korgs). This is less essential though if all of your keyboards have pitch and mod wheels. To use a pitch bend wheel means that one of your hands is not playing notes, so if you want to play on your master keyboard but have the sound come out of the other keyboard, why not use the pitch bend and mod wheel on the other keyboard, or just play the other keyboard entirely?
So, hopefully you can prevent all your keyboards from sending CC events other than the sustain pedal so you don't have to worry about your keyboards responding in unexpected ways when you use knobs and sliders.
So now that you have things set up in general, how do you make a specific sound? On your master keyboard, you'll want to make a set of programs/combinations with multiple voices in each. Each voice could either respond to external messages (which probably means setting it to a different channel from your keyboard's global channel), or internal messages (setting it to the same channel as your keyboard's global channel). To send notes from the master to another keyboard, you'll either set up MIDI sends separately from the combination itself (Yamaha keyboards do this) or using an extra voice on the combination (set to send externally but mapped to a region on the keyboard. Of course, use velocity switching, layering, or splits as you see fit. The second keyboard will be set up in a similar way.
I've just recently gotten a second keyboard and have put some thought into how to get the MIDI setup I want. Since someone else was asking me about it, I'll describe the setup in general and then specifically for one or two types of keyboards. The idea is to have a good MIDI setup for live playing with two keyboards that can be extended to use other MIDI-controlled gear as well.
The setup looks like this: both keyboards are connected via MIDI, and both are listening to different channels. One keyboard, which I'll call the master, has all the presets you need for a gig in order. When you pick a new preset on the master, it should send a *specific* program change to the other keyboard (which could be the same preset number as the one you've switched to on the master, but you're more limited that way). If your master keyboard allows it, you can use a footswitch to step through the program changes in order and have the other MIDI devices change programs accordingly. What you want to definitely avoid is having to change programs on more than one MIDI device and having to do it with mroe than one press of a button. You'll also want to be able to play on either or both keyboards and have either or both keyboards produce the sounds.
Firstly, you need to pick one of the keyboards to be the master. This *doesn't* have to be the better keyboard to play on (in my setup, it's the opposite); the master keyboard should be the one that is best at controlling other MIDI devices. Ideally, you want your master to be able to send program changes to all the other devices.
Next, MIDI connections. With two keyboards, connect the MIDI IN with each keyboard to the MIDI OUT of the opposite keyboard. If you have another MIDI-controlled devices (I use a Line6 PodXT guitar effects unit), hopefully one of the two devices other than the master has MIDI THRU, since that will be faster than a MIDI OUT A -> MIDI IN B -> MIDI OUT B -> MIDI IN C chain.
Next, MIDI channels. Each keyboard should be set to listen to data on different channel, or possibly multiple different channels depending on how well each keyboard does layers and splits. This may be done by setting a global MIDI channel, by setting MIDI channels in individual combinations/programs, or both.
What MIDI control data do you want to send to each keyboard? Obviously, knobs that send MIDI CC events on one keyboard may send them to another, and you don't want to tweak your synth pad and find out that you've also applied distortion to the piano sound playing on your other keyboard. In general, you don't want to send MIDI CC events at all, but there are exceptions.
One is pedals. You can't use more than two pedals at the same time, and most people aren't used to using a sustain pedal with their left foot, so you probably want to set it up so that one keyboard has the sustain pedal plugged into it but also sends the appropriate CC messages to the other keyboard. You might want this with an expression pedal as well.
The other exception is the pitch bend and mod wheels (or their equivalents, like the joystick found on most Korgs). This is less essential though if all of your keyboards have pitch and mod wheels. To use a pitch bend wheel means that one of your hands is not playing notes, so if you want to play on your master keyboard but have the sound come out of the other keyboard, why not use the pitch bend and mod wheel on the other keyboard, or just play the other keyboard entirely?
So, hopefully you can prevent all your keyboards from sending CC events other than the sustain pedal so you don't have to worry about your keyboards responding in unexpected ways when you use knobs and sliders.
So now that you have things set up in general, how do you make a specific sound? On your master keyboard, you'll want to make a set of programs/combinations with multiple voices in each. Each voice could either respond to external messages (which probably means setting it to a different channel from your keyboard's global channel), or internal messages (setting it to the same channel as your keyboard's global channel). To send notes from the master to another keyboard, you'll either set up MIDI sends separately from the combination itself (Yamaha keyboards do this) or using an extra voice on the combination (set to send externally but mapped to a region on the keyboard. Of course, use velocity switching, layering, or splits as you see fit. The second keyboard will be set up in a similar way.