MIDI stands for Musical Instrument Digital Interface and is used for nearly all modern music production. While it was invented in 1983, it has stood the test of time and is one of the most successful ways to connect devices in history. But many musicians tune out when they hear the term. With this MIDI primer, you'll be able to see how MIDI may help you automate your rig and spend more time performing.
How It Works
At its core, MIDI is just information that moves from one thing to another. For instance, right now you may be using a computer mouse. When you move the mouse around, it sends signals to the computer it's attached to. These signals may include how far it has moved to left and right or up and down. It may also send the position of the scroll wheel on top, or left and right clicks or double clicks. All this information is sent to the computer. Most computers know that when you move the mouse, a cursor on the screen should move. When you click the mouse, the computer takes where the cursor is pointed and performs an action. In essence, MIDI works the same way except instead of connecting you to your computer, it's connecting you to your instruments.
Just like the mouse analogy, MIDI can handle various events. These are broken down into common things that you do with an instrument. For instance, if you play a piano, your fingers press keys which traditionally would move hammers and strike the strings. How hard you play the keys will change the volume and tone of the sound. If you hold the key down, the string continues to ring out and when you release the key, the string is dampened.
Modern keyboards and instruments work in the same way by sending note events. These include note on and note off. Pretty simple, right? For every key on the keyboard, there is a different note. In addition, note on events can send how hard they are struck. This is called velocity. As long as the note is no, the sound would ring out until a note off event is sent, instructing the instrument to dampen the sound for instance.
Notes are just one aspect of playing an instrument. In keeping with our piano theme, you may have other ways that you can control the sound. For instance, you would have your foot on the sustain or damper pedals and turn it on and off. These can control the sound and are used in conjunction with the keys you're playing.
With modern keyboards, these pedals are considered control changes. So when you press the pedal, it tells the instrument that it's on 100%. When you release the pedal, it tells it that it's off.
Of course pedals are a simple kind of control. Another type may be volume. Let's say you're playing a beautiful grand piano. It may not have a volume knob, but you could adjust the lid position to change the volume and some of the tone. You could open it all the way, or close it completely. You could also position the kid to be held open.
Throughout MIDI you can use varying degrees of control. Velocity and the "value" of the control change can be expressed from 0-100%. Since MIDI uses bits and bytes, you have 128 possible options from 0 (0%) to 127 (100%). In the piano lid example, "0" would be a closed lid, "127" would be an open lid, and "64" would be half open.
This is all well and good for a simple instrument like a piano that only has one tone, but modern instruments can make many different sounds. These are often called programs, patches, or voices. Pressing some arrows or turning a knob could change the sound to a completely different instrument.
When you change the sound of a MIDI-enabled instrument, it's done using a program change. For instance, the very first program change in any device that uses General MIDI would be a grand piano sound. However, if we change to the second option, it would be an upright piano, etc. In this way, you can change the sound of your instrument by sending a MIDI value to the program change. Sending the value of "0" would change to an acoustic piano, value "1" the upright piano, etc. Keep in mind that computers, and thus MIDI, start counting at zero.
It's pretty obvious that a limitation you'll hit very soon is that there would only be 128 possible program changes. Today's modern instrument can make thousands and thousands of different sounds. How is it possible to switch to different instruments?
MIDI does this by placing program changes into banks where each bank could have 128 possible programs. Since we have 128 possible values, you could have 128 different banks. Some simple math means that you could have 128 banks of 128 programs each, or 16,384 programs. That's amazing, right?
Well, there are some musicians that didn't think so, or at least we can assume because in MIDI you can also have multiple banks or banks. In MIDI this is done using "most significant bit" or "MSB" and "least significant bit" or "LSB". These are scary computer geek terms, but the easiest way to think about it is that MSB is your first level of banks, and LSB is your send level of banks. Following the same math, you can have 128x128x128 possible programs or a little more than 2 million combinations. Phew!
One instrument doesn't make a band. You may have multiple instruments that you use for instance. MIDI supports 16 possible channels. This means that each channel has its own set of notes, controls, and program changes that operate independently of one another. The important thing to remember here is that you want to organize your equipment. If you're playing a keyboard, make that channel 1. Then make your guitar pedal 2, your drum machine 3, etc. You can then target or listen to specific channels without things getting confusing.
If you've gotten this far, you've probably started thinking about how to connect your MIDI-capable devices together. You've probably seen the MIDI connectors on the back of more than a few products. This is the older "5-Pin DIN" connector that is still a tried-and-true way to connect your equipment. This works using a simple "daisy-chain" technique where you connect the MIDI OUT port of one device to the MIDI IN port of another, and keep the chain going. Some devices implement a MIDI THRU port as well. This just lets you route the input directly to another instrument without the signal being modified. using this technique, you could connect 16 different instruments or devices in a chain and control them all using channels.
There's a problem with this way of plugging things in and that is... wires! While daisy chaining equipment is straightforward, it is sometimes not a convenient way to connect things together. The good news is that MIDI can be sent over different "transports". One of the most common ways you can see MIDI being sent is over USB. Many vocal processors and keyboards can be connected to your computer using a standard USB printer cable. Because computers can manage around 127 USB connections, you can connect a lot of equipment, especially with each controlling 16 channels or MIDI.
Another way is Bluetooth MIDI which now lets you control 16 channels of MIDI wirelessly. You can even send MIDI over a computer network making for really flexible solutions.
MIDI isn't going anywhere, and yet it's going everywhere. In 2020, the MIDI Manufacturers Association ratified MIDI 2.0. While it's outside of the scope of this primer, let's just say that what you've learned here today is just the tip of the iceberg. This new version takes advantages of new speeds in connection to offer even more control. Plus it's backward compatible with MIDI 1.0 that you've learned here today. We can't wait to see what the future holds with MIDI and the musicians that embrace it.