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What Is MIDI?

“How come I can’t hear my MIDI?”, was an inquiry that I was pelted with constantly when I taught at university. And 

with this inquiry came a rather simple answer; “You can’t hear your MIDI as it doesn’t transmit sound!” MIDI is actually a language or protocol that was developed that would ultimately tie musical instruments and other equipment together for the common purpose of performing, recording, and playing back musical performances. So if you can’t hear your MIDI, maybe this brief article can help you onto the right path!


Want to skip all of this and jump right into finding a controller? Watch this video and see if that answers your questions!



Musical Instrument Digital Interface

If you thought that MIDI was just a strange word that’s fun to say, you’re both partially right and wrong. MIDI is actually an acronym that expands into “Musical Instrument Digital Interface”, and that’s exactly what it is. Through a series of inputs, outputs, and throughputs, one is able to connect sometimes disparate instruments together so they can speak to each other and communicate a series of messages. Many times, a computer that’s coupled to a MIDI interface via USB or a controller/device that transmits MIDI over USB will be in the mix as well.

MIDI controllers come in all shapes and sizes today, but the most common is still the piano keyboard. Mini keys, slim keys, 25-48-61-76-88 keys, weighted, capacitance controllers… there are a veritable wealth of options and combinations in the keyboard universe! The keyboard paradigm has been in transition for some time, though, and while it’s still king, there are others to consider. Drum pads, grid controllers, gloves, gaming system controllers, drum triggers, and more have flooded the market in recent years, making the search for the perfect controller more daunting for some, and an addiction for others.

Musical Messages

At its core, MIDI is just a series of messages that are either played in real time and transmitted through ins and outs, or played back from a sequencer and transmitted through ins and outs. The most common of these messages are going to be note on/off and velocity. The note on message quite simply sends a message that note “x” is to be played when the key is pressed, while the note off message does the exact opposite. Another part of the note on/off message is the velocity at which the note is played and/or released. In the world of MIDI, velocity is just another way of saying how loud a note will be played which is informed by how hard the key is pressed. Velocity can also be used to change the timbre, attack, release, and countless other parameters of a sound or patch.

Other common controls are: pitch bend, modulation, aftertouch and sustain. Most of these messages are going to be global or common, meaning that all notes that are being played will be effected in the same manner. These rules can be broken, but a greater understanding of MIDI, and better equipped hardware is usually a part of this equation. Now you’re probably wondering what a few of the the aforementioned controls are, so I’m going to try to explain them as succinctly as possible.

Pitch bend – Allows the user to bend the pitch of all notes that are being played. Usually up or down, but this can be manipulated in most cases and also confined to a certain range. This is a physical controller (in most cases) that can be found on the left side of a keyboard. In most instances one will find a wheel or stick and sometimes a capacitance strip.

Modulation – This one is particularly fun! Think vibrato or tremolo and you’re on the right path. Can also be assigned or mapped to other parameters, but this also hinges on how deep you want to go. This also usually accompanies the pitch bend mechanism in the same form and they are most likely neighbors on the left side of the keyboard.

Aftertouch – Also like modulation, but happens via the keybed. Many keyboard controllers, and alternatives to the keyboard, have an extra level of control that can be engaged after the initial note is played. If you happen to press down on the keyboard after the initial note has been played and there seems to be an extra level of give, that is most likely the aftertouch mechanism. While usually global, some controllers offer what is called poly-aftertouch, in which aftertouch can happen on individual notes. This is a bit more advanced, and can be wicked fun with certain specialty controllers!

MIDI Values

The original MIDI specification or protocol is still in use today. What does this mean for you as a user? Well, it was really expertly planned from the onset. MIDI 1.0 has now been in use commercially since 1982 and all the wonderful vintage MIDI gear from the beats of yesteryear work with your favorite devices from today! The MIDI spec allows for 16 channels of communication both ways and generally has a resolution of 0-127 steps (7 bits). The resolution of pitch bend is bit different offering far greater resolution from 0-16383 steps (14 bits). Some of these rules can be broken with the use of MIDI interfaces (far more than 16 channels) and for the advanced users, writing scripts in certain programming languages or patches in certain applications will also allow for some rule-bending.

Connections and Communication

The most common connection today is going to be that of a MIDI controller connecting to a computer via USB, most commonly referred to as “MIDI over USB”. Most old pros are familiar with something different; the ubiquitous 5 pin DIN connection. If you’re new to the game, and currently have a controller that’s connected via USB, there’s a pretty good chance that your controller also facilitates the standard 5 pin connection. Just look at Arturia’s KeyLab MKII below and you will see what I mean.

Arturia’s KeyLab MkII 61 Top View

Arturia’s KeyLab MkII 61 Rear View

Arturia’s KeyLab MkII 61 Rear Connections

Standard 5 Pin DIN MIDI Ins and Outs

The KeyLab connects to your computer via USB, but also has a standard 5 pin in, and out, that will allow you to connect to other MIDI enable devices that don’t employ USB connectivity. This is a huge plus, and for those of you that are scouring the vintage market for drum machines, rack synths, samplers, and other devices, this will allow you to sequence vintage pieces using your current favorite DAW. The image below illustrates what a MIDI setup might look like today.


Connect the dots if you will, and follow the MIDI signal flow!


  • Green dots: These are the USB connections from the master controller and MIDI interface to the computer. This allows for two-way communication with your favorite DAW and other devices in the setup above.
  • Red dots: These are the connections from the MIDI outputs of the MIDI interface to the MIDI inputs of the synth module, synth and drum machine in the setup on the left. The MIDI outputs will send performance information, whether it be played in real time, or from the sequencer on the DAW to the MIDI inputs on the devices on the right. If connected properly, the devices on the right will play the corresponding note that is played on the master controller and/or sequencer.
  • Blue dots: These are the MIDI connections from the outputs of the devices on the right to the inputs of the MIDI interface on the left. The devices on the right can also send MIDI information to the computer via the interface. Many devices/instruments have various continuous controllers (CC) that might send information that is recordable into a sequencer. Sweeping filters, effects, sustain, and more can be sent both from and to devices if the MIDI setup is functioning properly. Other parameters can be sent from these devices as well, such as system exclusive messages which can restore a synth or drum machine to a certain state for a project.

(Please note that in the example above, the MIDI interface is exactly that, it transmits MIDI, not audio. It should also be noted that many audio interfaces can act as a simple MIDI interface adding one in and one out, both of which are standard 5 pin connections.   The setup above is not indicative of all setups! Many just employ a controller and a computer in their MIDI studio, while some might have a standalone sequencer, keyboard/synth, and drum machine that omits the computer altogether! Since MIDI is a common language, there are an infinite number of setups that can take place across thousands of instruments and other devices.)


MIDI Now and in the Future

MIDI is literally everywhere today. The amount of music applications that can be found on IOS and Android devices is staggering, and they all employ MIDI. Many controllers will work on these devices, and in some instances will even use the device as a power source. The MIDI 1.0 spec is and has been strong since 1982, but the 2.0 spec is in the works and many of the major hardware and software manufacturers are leading the way. All of the major operating systems currently support MIDI and the drivers and definitions for most instruments/devices already exist within said operating systems. The amount of specialty controllers that exist today is staggering, and many are customizable via MIDI, or when ordered, as in, made-to-order… killer!

More Questions or More Confused?

No sweat! Just use the form below or call and we will help get you sorted out. Looking forward to hearing from you!


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