In a previous article I wrote the basic definition of MIDI (Musical Instrument Digital Interface) and how modern musicians can use it in their independent productions. This time I’ll be writing about the technical side of MIDI, including the MIDI ports that are available, MIDI channels and how to use them, and the general MIDI standard that allows a MIDI file to be read consistently across a variety of MIDI-compatible instruments ( hardware and software).

midi-ports

Like any other technology related to audio or music, MIDI has an IN and OUT port. To explain the use of these two ports, let’s use the example of a MIDI keyboard and a computer (a MIDI to USB converter for the computer is required in this case). The keyboard’s MIDI OUT port is connected to the computer’s MIDI IN port. This means that the keyboard sends MIDI data to be played or recorded within the computer. Vice versa, the keyboard’s MIDI IN port can be connected to the computer’s MIDI OUT port, allowing MIDI data recorded within the computer to be sent back to the keyboard so that the keyboard can play the MIDI data (this means it can be recorded playing, editing the MIDI data in music software, and then playing it back on the keyboard and recording the audio that comes out of the keyboard for a better edited performance).

In addition to MIDI IN and OUT, there is a MIDI THRU port that is sometimes available on a MIDI instrument. MIDI THRU works to pass MIDI data received at the MIDI IN port to another MIDI instrument or device. Let’s take for example that the keyboard receives MIDI data from the computer at its MIDI IN port. If your keyboard has a MIDI THRU port, you can continue the data you receive from your computer to the MIDI IN port of another MIDI instrument. This is useful for chaining multiple MIDI instruments that receive data from a single MIDI OUT port on your computer (for example, to play multiple string parts using different string sounds on different keyboards).

In the latest technology, keyboards can be connected to computers via a direct USB connection without the need for a USB to MIDI converter. The downside is that it limits your ability to chain multiple MIDI instruments together.

MIDI channels

There are 16 MIDI channels for each MIDI port. That means that any MIDI port can send and receive 16 channels of MIDI data. Each MIDI channel contains all the MIDI information about a particular track. For example, if Track 1 is Acoustic Piano, then MIDI Channel 1 will contain note pitch, note duration, sustain, and other performance data to be played by a sound source. The sounds played are determined by the bank and patch number within the MIDI channel. For example, using the General MIDI standard, acoustic piano is always patch #1 and acoustic (nylon) guitar is always patch #25. There are 128 patches in all.

Having 16 MIDI channels per port allows you to compose a song using 16 different parts. For example, you can use channel 1 for the melody part using a saxophone sound (Patch #65 Soprano Sax), create the compilation part using a piano (Patch #5 Electric Piano 1), and compose the rhythm part using the bass (Patch #34 electric bass finger) and drums (using MIDI channel 10, a channel that is reserved especially for playing percussion sounds regardless of the patch number you program). If you need more channels, then you need more MIDI ports!

General MIDI (or GM) Standard

The GM standard is the standard used to be able to play MIDI files consistently between different MIDI devices. I mentioned earlier about patch numbers and MIDI channels. These patch numbers contain the type of sound to be played (#1 for acoustic piano). In order for another device to understand that MIDI Channel 1 is MIDI data for a piano sound, it applies the GM Standard and confirms that Patch #1 is a piano sound (it will then call its own version of the piano sound, sometimes this may sound better or may sound simpler depending on the internal sound synthesizer used to play the MIDI data). Most keyboards and software when saving MIDI data do so under the GM standard. I hope this article can help you to improve your understanding of modern digital music technology. For your musical success.