There's a YT video from Espen Kraft (the title is about Midi SysEx) which demonstrates one thing that this box is very good at. You can map a MIDI event from one device to send a SysEx string to another device. That's really the only thing this box is good at -- Mapping one thing to another thing.

The device processes incoming MIDI messages using its own custom programming language. It is not easy to use. The software looks like a Windows 3.11 app. If you're on a Mac, the software runs under Wine32on64 emulation, and it's not particularly stable.

The programming language is bizarre. There are only seven commands: Filter, Map, Trigger, Define a sequence, Define an Event in a Sequence, Turn a Setting On/Off, and Store Incoming Value In Variable. You can use those commands (aka 'settings') to write a program. The max length of the program is 32 commands, and you'll use that up very quickly because simple things require a LOT of commands.

If you aren't a software developer, good luck. If you email support they will respond and try to help. If you explain the problem to them you could probably get them to tell you exactly what to do to accomplish a simple mapping/routing task.

If you are a developer like I am, you might think for a second that the Event Processor has potential for doing cool stuff. But on further inspection it's pretty hopeless.

The way it works is VERY strange. Every command refers to the last incoming message. Even if you filter out all messages, the commands still operate on the incoming message as though it was not filtered. You can't modify the incoming message unless you're sending it. That is, you can remap a message to another message, but the message on the stack doesn't change. You can't change anything without sending a message, so you actually have to create more MIDI traffic and do some kind of loopback routing with your external hardware just to modify values.

You get eight 'variables' to use, but you can't do anything with them except store an incoming value then compare other incoming messages against that value. You can't increment or decrement a variable. You can't use a variable in a jump statement. There actually isn't a jump statement. There's just a command called "Define a sequence" which lets you define a sort of rotation of events that happen when a given message arrives.

The device is staggeringly weird. It was obviously designed by somebody very technical, but ... technical in a sense that they probably did some soldering on a Commodore 64 or a Juno 60 back in the day. Not technical like they could create a rational pipeline for processing MIDI events.

I'm not exaggerating when I tell you that anything you want to do with the Event Processor, it would take less time to build your own Arduino device to do it instead. Or if you're decent with Python, you could get something like a Mio XM/XL which you can plug into any computer and get MIDI-over-USB access to all the ports, and you can write a script (Python's Mido library is good!) which can do literally anything you want.

I like MIDI Solutions. I'm a big fan of their Quadra Thru. I'm not so much of a fan of their Merger products because they blindly merge clocks, but they're still useful.

But the Event Processor blows my mind. From a technical perspective, it's difficult to understand what they were thinking.

They created a programming language with no flow control and no arithmetic. The only conditional statements are "If the incoming message matches X do Y" where X can only be a static value or a variable, and variables can only have a value stored from an incoming message. So the only way to iterate anything is to use some kind of ridiculous hack -- like incrementing a variable by sending the value and mapping it to a higher value then routing the Event Processor back into itself using other external hardware.

The simple routing I wanted to do ended up requiring two Event Processor Plus boxes. It was a TOTAL mess and still didn't do what I wanted. I returned them both and got a Mio XM from Sweetwater and wrote a Python script in an afternoon that did everything I wanted.

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The MIDI Solutions Event Processor Plus is a truly fantastic MIDI accessory that translates, filters, or otherwise modifies one MIDI message into another. I first got two about 8 years ago and used one to sequence the drums of an Akai XR20 from an original Novation Circuit. I had my MIDI note velocities translate to different MIDI note numbers so instead of step sequencing with note numbers I was assigning notes' velocities. After that I used one to control the MIDI NRPNs of a Roland TB-3 from a Behringer BCN44 for a live set. This worked fantastically but I couldn't figure the programming out on my own and I didn't. John Fast over at MIDI Solutions is an invaluable resource. He's the founder and a wonderful company representative. If you have an Event Processor string you are trying to program, he will take your conditions and very quickly get back to you with a file for you to program your Event Processor or Event Processor Plus with at no charge. Most recently I wanted to control program changes on a Modal CraftSynth 2.0 from one of the macros on the MIDI lanes of a Novation Circuit Tracks BUT also have it ignore repeated receptions of the same signal value. John once again helped me with this and I have been a happy camper ever since. I have had luck programming my own Event Processor strings with the software editor but sometimes it's just a bit too confusing. MIDI Solutions' customer support is top notch. Long live John Fast. I love my Event Processor Plus and for creative MIDI control it is a must.

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The MIDI Solutions Event Processor Plus is exactly what you need if your keyboard or MIDI accordion doesn't transmit the MIDI events you need. I needed my left hand to trigger drum sounds and this device works perfectly. It made a huge difference in my live performances. Love it!