Chapter 3. In the Digital Domain

3.4. MIDI

What is MIDI?

We take a small detour from our signal path. So far, the sound has been produced and recorded in the DAW. It might have been processed, changed, altered, or modified. Or not. But what if you want to add another instrument? Say that you wanted to add a flute to a song you are working on but you cannot play that instrument. Composing music is one thing, and playing that composition with all the planned instruments is another. A Musical Instrument Digital Interface (MIDI) might prove useful in this case: it will allow you to create sounds representing any instrument from a MIDI instrument called a controller. You need three things to make it work: someone performing with the controller, a way to communicate between the controller and the computer, and a sound representing the desired instrument, stored on the computer.

The first item is taken care of very easily: you can buy MIDI controllers for dirt cheap, or even ask your smartphone to do it for you. The most common type of controller is the keyboard-type controller. There are also wind-type MIDI controllers, allowing for a very rich range of note expressions. Percussion controllers allow you to play drums on a “real” instrument and modify the drum sounds later.

The second item is where MIDI comes in. MIDI is a messaging standard which communicates note information digitally. Amongst others, MIDI messages contain the following items: note number, note velocity, note on timing, note off timing, volume, pitch-bend and channel (16 channels maximum). Notes range from C1 (around 8 Hz) to G9 (12.5 kHz). This information can be encapsulated in a file with the SMF (Standard Midi File) format. Where is the instrument information? It is not included in MIDI. MIDI only contains note information, not instrument information. A lot of people associate MIDI with 80s video game music sounds: that is only because computers have a very basic set of sounds in their sound library, so when played with default PC settings, MIDI sounds awful.

How do I use MIDI?

However, and that is where the third item comes in, sound libraries (also called sample libraries) nowadays contain hundreds of thousands of sounds, from percussion to strings to guitars to voices to winds to special effects. If it can be recorded, it can be sampled. The process of creating these samples is extremely time-consuming: you record each sound multiple times in various conditions so that when it is played by the computer, it sounds like a real instrument. In the more expensive sample libraries, you even find the same instruments played in different manners, like for example a violin played pizzicato or a guitar played muted. The only thing you need is a piece of software to play those samples per the MIDI information contained in the MIDI data transmitted from the controller – yet another use for your DAW.

This is how you would create that flute track in your song. First, get a MIDI controller and hook it into your audio interface – that is why some of them have a MIDI IN connector. Second, open your DAW of choice, add a track and prepare it for recording. Third, perform the flute part on the MIDI controller while recording it on the computer through the DAW. What happens if you now press the play button in your DAW? Nothing. Why? You have not told the DAW with what instrument it needs to play those recorded MIDI notes. Add a sample-playing plugin to the track, select the instrument et voilà, you now have a flute leading the way in your Swedish death funk song.

The power of MIDI resides in the fact that it is very flexible: you can use it with any DAW, with any MIDI controller, with any sample library. You could also buy a computer or smartphone application to generate MIDI notes (and music scores!) for you –if the format described above is respected, you are good to go. Because sample libraries are recorded so well, it is becoming increasingly difficult to tell a sample from the real thing. There are exceptions, of course (stringed and wind instruments come to mind), but for most intents and purposes, a single sample will do just fine.


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