MIDI (musical instrument digital interface) was developed to provide standardized communication between synthesizers. Today, it is much more than that and is found in computer, video games, effects processors and more. We’re primarily focusing on how to use it in music production—specifically with synths.
During the late 1970s and early 1980s as synthesizers became more powerful and polyphonic, controlling synths became more and more of a struggle. Traditional methods of using control voltage (CV) and gate signals was particularly problematic due to inconsistent CV requirements among the various manufacturers. Additionally, a single pair of CV/Gate connections could only send one control signal at a time. CV is inherently monophonic. Other control mechanisms had been developed, but these were strictly proprietary to each manufacturer.
MIDI solved these problems. In 1983, Dave Smith and Ikutaru Kakehashi demonstrated MIDI control between a Sequential Prophet 600 and a Roland JP6 promoting collaboration among synthesizer manufacturers.
MIDI’s original connectors are 5-pin DIN connectors. While other physical connections (USB, Firewire, etc.) are able to carry MIDI data, the original connectors are still widely used. Three different connections are possible: IN, OUT, THRU. Generally, a controller (like a keyboard or sequencer) is connected from its OUT jack to another device’s IN jack.
MIDI Thru duplicates the information arriving at a device’s IN jack and passes it back out to some other device. This way several devices can be controlled by a single controller.
MIDI sends its information on 16 channels. Using the connection method mentioned above, the devices connected to a controller can be configured to listen on one or more of these 16 channels and ignore information on others. Maybe a sequencer sends piano information on channel 1 and drum information on channel 10. The piano module and drum module in the chain are then configured accordingly.
MIDI organizes information into various message types. While not an exhaustive list, here are some of the most common message types:
MIDI also has provisions to keep everything sync’ed together. Sync messages are not sent on individual channels. All devices receive sync data unless configured to ignore it. Sync options include MIDI Timecode (MTC), MIDI Clock and Song Position Pointer (SPP). When syncing from a computer, it is best to configure your DAW to send either MTC or MIDI Clock and SPP. Transmitting both can cause double notes and hiccups.
Most audio interfaces offer a set of MIDI IN/OUT connections. This is okay when you only have a couple of devices in your MIDI setup. But, once your collection expands and you need more than 16 channels, look for a MIDI interface with multiple ins and outs. Mark of the Unicorn (MOTU) still has a few of these available.
The authority on MIDI is midi.org. Lots of documentation and helpful articles are now available on the official site. Additionally, consult the user guides for your synths. You’ll be surprised how much you can learn from the manuals.