Since the start of 2021, I've been using a Kurzweil PC4 in a cover band. These are some notes mainly on points that have confused me.
The PC4 is best thought of as a MIDI controller in a package with 16 MIDI modules, one responding to each MIDI channel.
In Program mode, the channel up/down buttons allow you to work with one channel at a time. External keyboards can control of any of the channels and any bank/program changes they send, for example, will affect the given channel.
(Detail: internally I believe Program mode is actually implemented using a special multi (maybe 2046 PC4 Control?).)
In multi mode the controller becomes more like 16 separate MIDI controllers, each with its own zone, each zone transmitting to your choice of channels (locally or over MIDI or USB, as you choose). External keyboards can still transmit to any channel but I believe bank/program changes are ignored for channels which zones transmit to.
On entry to multi mode the PC4 sends a flurry of MIDI messages to choose programs for each channel and set initial parameters. It sends another set of set of messages on exit. The messages sent on entry and exit are mainly determined in Multi edit mode by:
The latter is especially important. When switching from one multi to another, parameters for the 16 MIDI modules aren't automatically reset to defaults; their values persist. So if one multi leaves those parameters at undesirable values, that can cause problems for the next multi.
If (like me) you typically use one multi per song, a typical issue is that you start a song and suddenly find you're not getting any sound from one zone. This kind of problem may show up for the first time playing live, even though the multi worked fine in practice.
How can this happen? Suppose for example you had CC pedal 1 set to control expression on channel 3, and that you ended that song with expression turned all the way down. The new song is the first one you've played that also uses channel 3, and expression on that channel is still set to 0. So the problem only manifests when you play these songs in that order.
You might try to fix that problem by making sure the new song has a controller with an entry value set to a more reasonable default. That will work, but it's not ideal if for example the new song doesn't already have a controller assigned to the problematic parameter. You could add such a controller, and even set Scale and Add values so that in practice it does nothing but sets an entry value. But this gets cumbersome especially if you try to do this for every single parameter that a previous multi might have left in a bad place.
Better is to make sure that any muli that uses a controller always uses the controller's exit value to return the parameter to a reasonable default.
(Warning: if you ever try to control the same parameter from multiple controllers, you need to make sure only *one* of them sets entry/exit values; the other controllers should have entry/exit values of None. Behavior is weird (possibly buggy?) otherwise.)
A program change message normally just changes the program associated with the channel it's changed over. Sometimes you'd instead like to choose a multi. I know of two ways:
Occasionally I want to change a multi and then immediately send another message to adjust some parameter. I've found the latter doesn't work reliably unless I insert a small delay between the two. I believe what happens is that changing multis actually requires the PC4 internally to send a whole ton of MIDI messages, and if my second message arrives while it's still in the middle of that process, my message may get overridden by a later one.
I usually use the PC4 with a Behringer DM12 above, connected to the PC4 with two 5-pin DIN MIDI cables. Depending on the song, I may use the DM12 just as a MIDI controller, or may use its own internal sounds. I configure this all using multi mode on the PC4 as follows:
I set the DM12's RX channel to 15 and TX channel to 16.
One of the zones in the multi is set to transmit to MIDI only, channel 15. That zone is muted (and maybe Note Map set to Off just for good measure), EntryProgChng is set on, and MIDI Bank/program is set to choose the right patch on DM12. For multis where I want to use the DM12 purely as a MIDI controller, I use a custom patch that is completely silent. (It'd probably be cleaner to put the DM12 in local mode, but this seems to be easier.)
For any PC4 sound that I want to play from the DM12, I create a zone with Input Channel set to 16. It's possible to create multiple such zones to split and/or layer sounds across the DM12 keyboard.
The PC4's channel 16 should also be set to program None. Probably I should use a multi zone to make sure that's always true, but I don't, so occasionally I forget and leave some program on channel 16 and wonder why the DM12 is triggering some sound it shouldn't be.
Sometimes I also want PC4 controllers to affect the sounds I'm playing from the DM12: for example, I might want to play strings from the DM12 and use a PC4-attached expression pedal to fade them in and out. This is a little more complicated. You might think that this was just a matter of configuring controllers for the zone you created above. But the Input Channel setting on that zone means it only gets MIDI from controllers on the DM12 itself.
So, instead you need to create a new zone with Input Channel None, Destination Local, and MIDI channel set to the same channel as the zone you created above. Now you have a zone that takes input from the PC4 and sends MIDI to the channel you care about, and you can configure controller as you'd like. But you *don't* generally want this channel sending program changes or note ons--so set "Note Map" and "EntryProgChange" both to off.
Warning: this doesn't work for all parameters. For example, "mute zone" actually affects only the zone itself--it isn't sent to the MIDI channel.
I've found this limitation occasionally frustrating, for example if I want to switch the DM12 back and forth between playing strings and horns. You could imagine setting volume to 0 to mute a sound instead, but unlike "mute zone" that cuts off already-playing notes too, which isn't usually what you want. One workaround is to use controllers on the DM12 (for example, a pedal connected to the DM12) instead. Maybe individual keys themselves could be used as controllers (think of the preset keys on a Hammond).
Another option might be to use a split and octave up/down keys on the external keyboard to move it to either side of the split; it would require multiple presses and be easy to get lost, I think.
Can a riff trigger a midi sequence that sends a program change? I doubt that works, but maybe.
You can take a screenshot by pressing softkeys 1 and 4 together.
There's a developer mode which will do things like modify the normally unmodifiable built-in programs and multis. That's an easy way to get yourself into trouble, so they ask people not to publish it, but you can probably ask someone.
Occasionally I'd like to send more than a program change to the DM12 on multi entry. I wonder if you could do this with riffs?
If you connect the PC4 to a laptop with UB without any flash drive plugged in, you'll see there's an empty 66MB FAT filesystem. I wonder what that is? There doesn't appear to be any way to access it from the PC4 itself.
The sliders are a bit more convenient to use as drawbars if they're color-coded the way Hammond drawbars usually are. If you look around you can find aftermarket caps that accomplish that. They pop on and off easily so it's an easy thing to change.
The PC4 manual is missing a lot of details in some areas. But also a lot of stuff is the same as on previous products. If you want more details on how some effect parameter works, you may find what you need by digging through older manuals on Kurzweil's website.
Previous Kurzweil models apparently had a "button mode" that would let you use the numeric keypad buttons as arbitrary controllers. As far as I can tell that's been removed from the PC4.
I've occasionally encountered actual bugs. Kurzweil's been responsive. They've all been fixed, and I don't know of any right now.
forums.godlike.com.au can be a useful source.
Be careful about choosing compatible TRS/continuous pedals (including sustain pedals with half-pedal support), they don't all work well.
It looks like you should be able to change the behavior of the sustain pedal by editing the multi, but actually it's hard-wired: attempts to modify the behavior of Sw. Pedal 1a while it controls Sustain (MIDI 64). You *can* change the behavior of Pedal 1a when it controls something else, or of other physical controls when they map to MIDI 64. But if you have the combination of the two and attempt to, say, edit the on/off values or change it from momentary to toggle--that'll be ignored.
I don't edit programs as much as multis, but one thing I've noticed is that the RES NOISE with a high Noiz Q will clip before it really gets to the point of whistling. It's less forgiving in that way than a real analog synth. That seems to be typical.