While that is a lot to cover under the entire umbrella of what MIDI is, For our purposes of discussing MIDI for guitar can be considered something like a "Networking" standard for gear in a way. Basic MIDI 1.0 has 16 channels on which it can communicate with a standard communications protocol over DIN-5 cables called "MIDI Cables". I've owned a LOT of equipment like this including 2 Digitech RP-series effects, my Line6 HD500 I currently use, my old Behringer V-Amp Pro I used in the 2000s. And 90% of what we will be discussing here - is how MIDI equipment is wired up, how footswitches are programmed, and how we can control multiple devices.

The simplest purpose of MIDI for us, using digital effects processors, is to connect them to a computer. This is done a few different ways. USB is one of them, which then nullifies this whole document (unless you're building an 80's style Rack Rig and making use of MIDI to control multiple devices from one footswitch). But what if you're using an older MultiEffect Device or Amp Modeler that has the two or three DIN-5 Jacks on it - well, that's where this document comes in.

These devices typically have 2 schemes - one is 2 DIN-5 ports - one is a MIDI IN, one is a MIDI OUT/THROUGH. This is more common on newer devices with MIDI Ports, and usually the MIDI OUT is configured as a MIDI THRU by changing the settings in the firmware of the device somewhere (you'll have to read your manual on how to do that). The other scheme has dedicated In/Out/Through ports - so 3 total. On those, for a simple one-device setup for editing patches, you'd just connect the MIDI Out from the MIDI cable/USB to MIDI Adapter, to the MIDI IN of the device, and then the MIDI IN from the MIDI Cable to the MIDI OUT of the device.

There are two types of cables you can use to do this. The current way is a USB-to-MIDI Adapter, it has a USB-A connector on one side, and then 2 DIN5 MIDI connectors on the other side marked MIDI IN, and MIDI OUT. The older style, which I still use because I have a 386 and 486 PC that still have the old 15-pin game port - takes that 15-pin game port and splits it into a game controller port, and then the two DIN-5 MIDI IN/MIDI OUT jacks. You have to wonder how many people who played synth in the 80's or 90's were playing computer games after Soundcheck. The older style cables can be a bit harder to find, but might be worth it if you are really wanting to have an authentic "retro rig" of sorts.

DIAGRAMS OF VARIOUS MIDI SETUPS

Each device is assigned a number on the MIDI network - and that number is what is basically known as a "channel". So when a MIDI Command is issued, it's issued on that channel for that specific device(s). Say you need to change patches on your Behringer V-Amp Pro which is Device #2 on a MIDI Network, and your Footswitch is Device #1 - The Footswitch will send a MIDI Command on Channel 2 to your V-Amp to change patches and which patch to change to - simple as that.

MIDI can also issue commands more than one at a time, allowing for some pretty elaborate patch changes if you need it to. Say maybe you have a V-Amp, a Virtualizer 2024P, a MIDI Switchable Tube Amplifier, and a MIDI Footswitch - now the V-Amp is on 2, 2024P is on 3, and the Amp is on 4, and the Footswitch is on 1. So you want to change from your distortion channel with a light reverb on the Virtualizer and some compression and chorus from the V-Amp - over to the clean channel with heavy reverb and delay for some etherial thing - then MIDI can send commands over all these different channels to switch all these devices over to their desired presets to get the sound you want. That's the whole point - being able to enhance your creativity by running multiple digital devices together to create sounds with electronics you could not otherwise create.