There seem to be a new surge of MIDI enthusiasts on the forum again, so I thought I’d revive some MIDI concepts, in short form. I’ve used MIDI for a long time, so I likely take much of it for granted and I’m only human. I apologize in advance for anything FUBAR (I’ll update this post as needed).
A physical machine (e.g. a hardware synthesizer) or virtual (e.g. a VST plugin or a host) application capable of MIDI communication.
A physical or virtual connector on a device. There are three types: In, Out or Thru.
A device uses a MIDI Out to transmit data and a MIDI In to receive data. A MIDI Thru is used to relay data received on MIDI In to another device. (see diagram below)
An interface can have any combination of ports. E.g. a hardware synthesizer typically have an in, out and often a thru port. Such a device is considered to have a MIDI Interface.
There are also more advanced MIDI interfaces, e.g. Steinberg Midex 8 (a USB MIDI interface) has eight ports in and eight ports out. A good interface if you have many hardware devices.
A physical (typically a 5-pin DIN cable) or virtual communications pipeline between two interfaces. Many recent devices talk MIDI over USB.
A series of devices connected with a chain of MIDI cables. (see diagram below)
A cable is subdivided into sixteen virtual pipes, called channels.
The concept of channels is what enable synthesizers to be multi-timbral (e.g. HALion 4 or a typical rack synthesizer).
An event, or message, containing MIDI performance data or other MIDI information. E.g. Note On, Note Off, Modulation Wheel, Pitch Bend, etc.
Messages are transmitted from a device via its out port. The messages will be received by devices connected to the chain (via their in ports) and listening to the channel associated with the messages.
I.e. pressing a key on a keyboard is an event, generating a Note On message transmitted over MIDI to other devices. Recipients can then emulate the event, using the same key and velocity.
There are also certain events not associated with MIDI channels.
Shows how three MIDI devices typically are connected with Cubase, using a simple in/out interface on the computer.
You play the master keyboard and the currently selected track dictates which device will receive the MIDI data from you playing. When devices are chained, like the three shown above, MIDI channels are an important consideration.