The MIDI Interface

Any decent synthesizer these days comes with a MIDI Interface built into it. Most computers today come with some sort of Sound Card pre-installed that is capable of functioning as a MIDI instrument using General MIDI or GM. You will need an adaptor cable, though, to plug external MIDI instruments into the sound card so they can be controlled by the computer. These adaptor cables are generally a “Y-cable” that plugs into the sound card’s joystick port and splits to replicate the joystick port and give you a MIDI IN and OUT port as well.

There are also dedicated MIDI Devices that you can buy for your PC that are considerably more flexible and cost between £35 and £300, depending on how sophisticated a MIDI interface you need. The most basic, yet more advanced than a sound card-based MIDI Interface, gives you a MIDI IN, OUT and THRU port or multiple OUTs like a MIDI patch bay – though not as sophisticated.

Owning a MIDI Interface by itself doesn’t do a whole lot for you. You must have some sort of sound-generating device. On the PC, a sound card has a built-in MIDI compatible sound device that can be accessed without any special cabling. Simply load a MIDI file and play it back. There are tons of MIDI files on the Internet! If your sound card is not one of the new wavetable types, then the sound that you hear will probably be a bit on the thin side. This is because the method in which the sounds are generated is not very sophisticated – relatively speaking, of course.

The low-end sound cards use something called Frequency Modulation Synthesis (FMS), which is a sound producing technology whereby simple waveforms (sine/square/triangular) are combined mathematically to produce complex sound waves. Wavetable Synthesis is actually method of synthesizing sound which uses high quality digitally recorded sounds ( samples) as building blocks to create more complex creations that can then be further modified with digital filters (like compression, reverb, etc.) If you will be using your PC as a sound-generating MIDI instrument (as opposed to just using for the MIDI Interface), I highly recommend that you invest in a Wavetable Sound Card. They only cost slightly more than a entry-level sound card and your ears, not to mention that base, animal rhythm that exists in us all, will thank you.

Most sound card MIDI adaptors only have two MIDI ports on them. One of the ports will be a MIDI IN port and the other will be a MIDI OUT port. If you are using only your sound card as a MIDI sound device, then you will never need to hook any MIDI cables to either of the two ports. If you will be using an external MIDI instrument such as a synthesizer or a drum machine with your PC, then you will need to take one MIDI cable and plug it into the computer’s MIDI OUT port and take the other end of it and plug that into the external instrument’s MIDI IN port. This allows the PC to send MIDI messages to your external instrument for playback. To record MIDI information from the external instrument to the computer, you will need to plug a MIDI cable into the external instrument’s MIDI OUT port and take the other end and plug it into the PC’s MIDI IN port. When you play notes on the external instrument, the notes will be passed out of the MIDI OUT port and move into the PC’s MIDI IN port. Using a MIDI Sequencer on your PC will allow you to record MIDI information into your PC for playback and editing. This is the most basic MIDI setup. It works very much like water running through pipes.

Let’s review the first two MIDI ports before moving on.

  • Messages arriving at the MIDI IN port are routed to the instrument’s internal sound-generating hardware.
  • A synthesizer will respond to messages from it’s MIDI IN port as though they originated on its own keyboard.
  • All messages that originate from an instrument’s keyboard or other on-board control is transmitted to the MIDI OUT port.

Now let’s discuss advanced MIDI setups utilizing the third, and perhaps most useful of the MIDI Interface ports – MIDI THRU. The next section also describes how you can control multiple MIDI devices by assigning them one of the 16 MIDI channels.


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