MIDI was developed in the 1980s and soon became the standard protocol for representing and transmitting musical data to electronic devices. It’s easier to think of MIDI as a set of instructions. These instructions are sent by one device (usually called a MIDI controller) to another device that can interpret these instructions and produce the relevant sounds.
There are a large number of devices that can interpret MIDI data. These include electronic keyboards, synthesisers, samplers, sound cards and many others. In fact, you can input MIDI data into a computer and software can act as virtual synthesisers and samplers. Indeed, you can use MIDI to play a whole host of virtual instruments. This means a single individual can control an entire band worth of instruments from a single device.
Here’s a basic explanation of a MIDI controller communicating with a synthesiser:
- A key or button is hit on the MIDI controller
- A MIDI signal is generated called “Note On”. This contains information about what key or button was hit and how hard it was hit (called velocity).
- The MIDI signal is sent to the connected synthesiser.
- The synthesiser reads the MIDI signal and generates the sound related to that key or button at the volume level appropriate for how hard the key or button was hit. It keeps producing this sound until the key is released.
- When the key or button is released, another signal called “Note Off” (containing which key or button was released) is sent to the synthesiser.
- The synthesiser reads this data and stops playing the relevant sound.
There are other MIDI signals, for a full list click here.
A computer can take this data and input it into software called a sequencer. This allows the MIDI data to be edited and modified. In fact, you can generate MIDI data from scratch in these programs. Instead of having to play an instrument you can draw in the relevant notes and timings. This has made music production more accessible as well as made it easier to edit and construct tracks professionally. Interestingly, karaoke machines make use of this feature of MIDI generally and this allows them to quickly change the pitch of the same song for a different person.
The important point to note about MIDI is that it does not produce sound. The MIDI controller generates a MIDI message, sends it to the device it’s connected to and the quality of the playback depends entirely on these connected devices, not the MIDI signals. This means MIDI files are much smaller than audio files.
In the early days of the internet when download speeds were very slow, the smaller size of MIDI files saw them been used to play sounds rather than actual audio files. These were then interpreted by sound cards and sound was produced. The problem was sound cards back then had very basic MIDI playback. This created the perception that MIDI was a form of low quality audio, which couldn’t be further from the truth. As David Battino, writing for O’Reilly Digital Media, remarked:
When most people hear the word MIDI, they think of the annoying tunes that wheeze out of mid-’90s Web pages. Contrary to popular belief, MIDI doesn’t “sound bad”—it has no sound at all. It’s simply a communications protocol. No one says Postscript looks bad; the output quality depends on the printer.
Similarly, a well-crafted MIDI file played through a high-quality synthesizer sounds great. That’s something you hear every day, whether you realize it or not.
In today’s age, it’s much more common for sound cards to contain high sample quality sounds. However, the increase speed of internet connections has seen a decline in the sharing of MIDI files because it’s now possible to easily share the larger files containing fully produced audio.
Finally, let’s take look at the most common MIDI devices and, hopefully, remove some confusion surrounding them:
MIDI Controller: These devices don’t produce any sound of their own. Instead they have what is called “MIDI out” and send MIDI data to MIDI enabled devices connected to them. They most commonly come in the form of a keyboard. However, other MIDI controllers exist such as wind and guitar controllers. Drum machines and electronic drums are also very common forms of MIDI controllers.
They can also contain knobs, dials, pitch bend and modulation wheels, which either send additional MIDI signals to control panels of other devices (such as effects panels) or modify signals sent from the general buttons or keys.
A single MIDI controller can control multiple instruments. The lower register of a MIDI controller keyboard might control a synthesiser, the mid-section a virtual violin and the upper part a drum machine. For example, you could play the drums while laying down some guitar chords or play a bass line over the top of some piano chords. Of course, when recording it’s much more common to record each section separately.
Sound Modules: These are devices that produce or play sound, but don’t have an on-board controller for the sounds to be triggered. This means it’s necessary to connect a MIDI controller in order to use the device. They can be samplers, synthesisers or other devices. However, it’s important to note that a synthesiser or sampler can contain on-board controllers of their own and, therefore, meet the definition of both a sound module and a controller.
A clear example to give you a picture of the difference between devices with and without on-board controllers is to consider a computer mouse and a touch screen phone. The mouse needs to be attached to a computer which can read the data the mouse sends. A touch screen phone is part of the electronic device and sends a signal to its self. It doesn’t need to be connected to anything.
The great thing about synthesisers and samplers with on-board controllers is, in addition to producing or playing sounds; they can be connected to other devices and send forward MIDI data. This means the data can be sent to a sequencer for recording and their on-board controls can be used to control other MIDI devices.
Keyboards with MIDI I/O and Workstation Keyboards: There are also keyboards with MIDI I/O. This is where a keyboard controller is combined with a synthesiser. The controller doesn’t have to be connected to anything to produce sound since it sends the signal to its self like the synthesisers described above.
There are also workstation keyboards. These are the same as keyboards with MIDI I/O, but they also contain a sequencer. This means you can compose songs in the one unit (an example of one is the Korg Triton).
MIDI Interfaces: These devices have a number of slots for MIDI devices (controllers and synthesisers) to connect to and in turn the MIDI interface connects them to a computer or other device. These are useful if you have multiple MIDI devices to connect to your computer. However, audio interfaces have slots for MIDI devices and these devices generally work via USB in today’s age, so unless you’re planning on connecting a myriad of devices, a MIDI interface shouldn’t be necessary.