What MIDI is... A Primer.

MIDI (Musical Instrument Digital Interface) is a computer language. It's really just a set of digital instructions to tell another piece of music gear what to do. MIDI, unto itself, has nothing to do with the actual sound. It refers to the connection between your instrument, effect unit, drum machine, sound module, computer interface, or anything else with MIDI jacks on it. MIDI cables are used to connect these points. They are 5 pin round plugs with a detent for correct orientation.

 

MIDI Cable

The connections on the device are generally labeled "IN", "OUT" and "THRU". These connections are simply logical points that we use to connect an instrument you physically want to play (the 'controller') to the device you want to remotely control (the 'slave'). As we play the CONTROLLER, the signal created must go "OUT" of the controller, "IN"to the SLAVE so it can know what to do. The "THRU" connection passes the information along to the next connected slave's "IN" and so on. You can link as many MIDI devices as you have.

MIDI connections

Imagine your TV for a moment. Generally, it's connected to cable. How can this one wire carry 1000 different channels of programs to watch? That is mind boggling enough for me, but the TV itself (or actually the cable box) is able to choose which one of the channels you want to see by selecting that channel. MIDI operates similarly. Our CONTROLLER 'broadcasts' on any one of MIDI's 16 channels. In order for the SLAVE to respond to this information, it must be set to the same channel number.

Some people who had purchased keyboard gear from me in the past got all excited to connect MIDI jacks to other MIDI jacks in equipment they already had, only to find out nothing was working. Typically, I would soon receive a frantic phone call. Some of my past customers were under the impression that MIDI was the SOUND! It is not, so you must still connect the audio outputs of each keyboard and slave to an amplifier. MIDI only CONTROLS the devices...MIDI has no audio, only control information.

In its simplest form, connecting a keyboard's MIDI OUT to another keyboard's (or sound generating module's) MIDI IN, and matching the channel numbers, we can play the controlling keyboard and hear both the controlling keyboard AND the slave simultaneously. This was great for layering different sounds together, like the meat-and-potatoes piano/strings combination I used to use for the wedding band I played with years ago. At that time, keyboards weren't able to make several different sounds at the same time, so connecting two of them together through MIDI was the way to accomplish this.

So, if there's no actual sound going through these MIDI cables, what is? It's staggering how much varied information is actually pouring down these cables at speeds we perceive as instantaneous. In short, when a key is pressed on the controller, MIDI 'tells' the connected device to play that same key. At the same time, it's also telling the slave how hard to hit the note and how long to play the note until its release. Simple, right?

This is MIDI in action in its most basic terms. If we go to switch to a different sound setting on the controller, we will find that MIDI has sent a PROGRAM CHANGE command to the slave. There are 128 of these in MIDI. This causes confusion on many levels because we now have instruments with thousands of sounds in them. Rather than confuse the issue now (something to get into later), let's assume each keyboard has 128 sounds in them. Where the confusion lies is that all keyboards have different methods of listing out their individual sounds. Roland's famous 8 set method listed sound 1 as 1-1, or Set 1, sound 1. By the time we explored up to sound 9, Roland's 8 set system was calling it 2-1. Hopefully, you're getting the logic here. Roland's sound number 8-8 was really number 64. To get to the next set of 64 (if there were that many), there might be another level where you could access the next bank. Get the picture? Now, to throw a wrench into the works. Computers like to call the first number of anything counted with "0". Sometimes, we will see "PROGRAM CHANGE=0" on our keyboard or computer displays which actually means Sound Number 1. So, in tech terms, MIDI is capable of transmitting Program Changes "0-127"; another thing to be aware of if we are to begin looking at the actual computer data at some point. This was another phone call I used to get..."I keep setting my sound to #57-Trumpet and it keeps switching to #56-Orchestra Stab...What's wrong with it??"

Tons of other stuff can be transmitted through MIDI such as PITCH BENDING, MODULATION WHEEL, VOLUME, and much much more...that will be a topic for another time.

My advice is to get familiar with the MIDI menu of your instrument or device. How to change the channel numbers and other settings will be in that part of your instrument's setup. More advice? Connect stuff together and have fun with it. That's really the best way to learn what it can all do. Sometimes, people won't try things because they're afraid they will ruin something. Luckily, the only adverse reaction you'll get from your instruments is that they just won't do what you expect. Be sure your connections are correct and have some fun with combining sounds!