MIDI, MIDI and more MIDI! MIDI is a great tool for controlling electronic musical instruments. But how does it really work? How is it different from audio recording? Here are the basics.
The Musical Instrument Digital Interface was invented in the early 80s, as a way to create layered sounds by controlling several sound generators from one keyboard. As it turns out, MIDI can do this and much more. A MIDI sequencer provides a flexible and powerful way to record, edit and play back musical information.
February 25, 1999
MIDI is not a method for recording audio. It is a code that allows various musical devices to exchange information describing a musical performance. The master device tells the slave(s) what notes to play, and when. It has often been compared to the rolls of paper that are used by player pianos.
The basic unit of MIDI is the message. There are many types of MIDI messages, but the most basic is the Note-On Message. A Note-On Message instructs a device to play a certain note at a certain velocity. How the note sounds is up to the receiving device. Each MIDI message consists of 2 or more bytes. The first byte tells what MIDI channel the message is on, and what type of message it is. If it's a Note On Message, the second byte gives the note number, and the third byte gives the velocity. Velocity usually controls the volume of the sound, but it can be mapped to other parameters. If you will, all the responsibility for producing the note rests with the slave device, and the responsibility for organizing the notes into a complete performance rests with the master device. This separation of functions is what gives MIDI its great flexibility.
A MIDI master may be a keyboard or other instrument, or it may be a sequencer. The slave may be a synthesizer, sampler, drum machine, or actually anything that could be rigged up with a MIDI IN jack! The most obvious benefit is to create layered sounds by slaving several tone generators to one keyboard. But it is the sequencer that makes MIDI a musical tool of the first order. A sequencer (which may be a computer program or a stand-alone unit) records, edits, and plays back MIDI data. This allows you to separate the act of creating a musical performance from the act of playing it. Sounds may be changed, and so can their amplification, effects, etc. after the fact. Since MIDI data is so much simpler than audio, it is much more easily editable. A recorded MIDI performance may be transformed into almost anything, or a performance can even be created mathematically. MIDI sequencing has opened up whole new worlds of creativity for composers.
Studio owners (virtual and otherwise) find MIDI very useful. An old maxim of recording states that you always have more ideas than you have tracks available. MIDI can help you squeeze in a few more tracks. Let's say you have a four-track analog deck, and you want to record 3 tracks of acoustic instruments, and several synth tracks. By sacrificing one track for a sync code, a MIDI sequencer can be slaved to the tape machine. You can then record as many tracks of MIDI as you wish, and they will play back in sync with the tape. A lot of people use an electronic drum machine to set up a "click track", but you don't have to. The sequencer does not have to set the tempo, it just has to lock to the tape. The only drawback to not using a click track is that the display of measures and beats in the sequencer will not match up to the measures and beats in the music. So you see, you don't have to play in an electronic style to make use of MIDI. As long as you have 2 or more MIDI instruments, you can squeeze out more tracks using this old trick. Also, the MIDI tracks will not be recorded to multitrack tape. They will play back directly from the synths or whatever into the mixdown deck, meaning one less tape generation and a quieter final product.
In the virtual studio, the number of audio tracks is limited, so MIDI becomes particularly useful. Those precious audio tracks can be saved for guitars, vocals, and such. Products like Cakewalk Pro Audio and Cubase Audio are designed to let you combine MIDI tracks and audio tracks. Other popular audio-recording programs like SAWPro and Sound Forge do not handle MIDI internally, although they can use MIDI Time Code (MTC) to sync to programs that do. If you plan to do a lot of your work with MIDI, an integrated MIDI/audio package could save you a couple of headaches, but if you really want to be cool, you should have a wicked MIDI package like Cakewalk, a wicked recording program like SAW, and an editing package like Sound Forge, or Samplitude Studio.
To use MIDI with your PC, you'll need a MIDI converter. Most of the general-purpose soundcards include a MIDI converter, though not actual MIDI jacks. All you need with one of these cards is a little adapter cord. Older high-end audio cards, like the Card D have no MIDI converter, but many of the newer ones, such as the Wavecenter, do. See our reviews of audio cards to find out which ones include MIDI. Those with sophisticated MIDI needs may want to have a dedicated MIDI converter. The MIDI Express PC is a very powerful one, although now superseded by a (doubtless even wickeder) newer model.
