MIDI Basics



What is MIDI?

MIDI Stands for Musical Instrument Digital Interface. MIDI is a digital language that was agreed upon by major manufacturers of Electronic Musical Instruments. It allows Keyboards, Synthesizers, Computers, Tape Decks and even Mixers & Stage Light Controllers to talk to each other.

What has MIDI got to do the average person?

As long as you own at least a small keyboard that supports MIDI, it means that you have the choice to expand the system. The first step may be to connect the keyboard to the PC's sound card, such that the sequencing (arranging of the notes in a song) can be done in colour on a big screen instead of squinting at a small LCD panel (or blinking LED's)

How do I get started?

You may already have some components of MIDI already. All Sound Blaster compatible sound cards has the ability to accept MIDI signals and play the sounds. All you'll need is a Sequencer program (eg: MIDI Music Shop) and enter the notes directly via the computer's keyboard.

If you don't like entering the notes by using the mouse & typing, you can buy a music keyboard. A simple Yamaha or Casio one will do. The most important part is that the music keyboard must have a MIDI port at its back. The only other extra hardware you'll need is to purchase a MIDI Interface (I know there's a double "Interface" - it refers to a PC to MIDI Interface) that plugs into the game port of your sound card, and 2 MIDI cables.

What's the difference between a .WAV file and a MIDI (*.MID) file?

A *.WAV file is a digital recording of the sounds made by any instrument (including your voice box). It basically cannot be modified unless it is very short or you own a workstation. When a PC plays back a WAV file, it converts the numbers into the audio signal that's fed into the speakers. A complete song done in .WAV format is always very big.

A *.MID file contains what the composer (or the person who played it) did at his/her music keyboard. It keeps track of which note (key) was pressed, when it was pressed, for how long, and at what pressure. Playing back a MIDI file would need a device (sound card) that can generate the sounds of common instruments (eg: Piano, Violins, Drums) on its own. The note data is sent to the device, which then generates the sounds that was intended (or sometimes not intended). A MIDI file is comparatively very small and can be edited (including changing the instruments altogether).

However, a sound that is not in the memory of your sound card cannot be generated (unless you have SB32) - and that includes you voice. The quality of the sound is also dependent on the quality of the synthesizer on your sound card.

By comparison, a wave file is always true to the original instruments that produced the music.

What's General MIDI?

General MIDI is a standard adopted recently (comparatively) by many manufacturers. The original "problem" of MIDI is that if you took a MIDI file from one musician's studio to another's, they probably won't assign the same instruments to the same patch # (Instrument number). So a piano part may be played as a drum, a violin becomes a trombone...and so on. General MIDI is a set of rules such that the same patch # correspond to the same instruments. (eg: Patch 0 is always Grand Piano, Patch 40 = Violin) That is also the standard for Sound Cards too.

What are Channels?

The idea is that there are 16 channels in General MIDI, and that's also the case in most sound cards and synthesizers.

Different instruments can be assigned to different channels at the same time. So theoretically you can have a maximum of 16 instruments playing at the same time. The actual number can vary, because the sound card or synthesizer can only produce a fixed maximum number of notes at the same time. (eg: 32-voice polyphony means that you can only press 32 keys at the same time and hear them. The 33rd key you pressed will either be ignored, or the first key you pressed will be cut off) You can also use more than 16 instruments if you can "steal" a track (eg: Your harp only comes in at the introduction, so you can use the same track for another instrument that only appears later in the song on the same channel). All 16 channels are transmitted in one MIDI cable.

What are tracks?

You can use as many tracks that the sequencer program allows you to. (Usually more than a hundred) A track contains the events (i.e. the things you did; eg: what key you pressed at when & for how long) you want to put inside. For example, you may want to do a very complicated Grand Piano part. You can record the right hand part in track 1, and then record the left hand part in track 2. If you make a mistake while recording the left hand part, you don't have to worry about the right hand's - it's stored seperately in track 1. Then you can assign both tracks to channel 0 (Grand Piano in General MIDI - mentioned above). The end result will sound exactly like you played both hands at the same time! (*Note: percussion instruments are stored as a single "Instrument". Different keys correspond to different drums)