What is MIDI?
(article by Paul Alan Smith 02/02/02)

MIDI is an acronym for "Musical Instrument Digital Interface".  It was originally created in 1983 to enable synthesizer keyboard players to transmit keyboard "events".  MIDI synthesizers, samplers, drum machines, and computers can be connected using special 5-pin MIDI cords.  Sounds on another device (synthesizer or sampler keyboard or module) can be remotely triggered.  With a keyboard connected to a computer via MIDI, performances can be recorded, multi-tracked, processed with effects, edited, and mixed-down in a variety of sophisticated digital audio software programs.  

Game systems like Nintendo and Sega have long used MIDI technology to keep their music file downloads smaller and quicker.  With the advent of the internet, MIDI files have become important as a music source that downloads quickly.  QuickTime players contain a built-in MIDI player and can even display "karaoke" MIDI files that highlight text lyrics in time to the music.  In professional recording studios, MIDI is often used to create the original tracks for hit songs, helping humans stay on the beat (or "IN SYNC") when they overdub live performances.  Some of the MIDI tracks themselves often make it to the final CD mix (like "NSYNC"). 

Using MIDI to Create a "One-Man-Band"

• The main "controller" keyboard itself, assigned to Channel 1, outputs a "Grand Piano" sound.
• Every key played below the "middle C" key sends MIDI to the second keyboard on Channel 2 which is set to a "Fretless Bass" sound.
• Every key from "middle C" up triggers the synthesizer module on Channel 3 which outputs a "Trumpet" performance.

When the performer plays on his keyboard with 2 hands, the audience hears the left-hand part (the green keys) as Fretless Bass from the second keyboard, the right-hand part (red keys) as Trumpet from the module, and both hands as Grand Piano from the performer's keyboard.  If each audio output from the keyboards and module are sent to different speakers, it sounds like a perfectly synchronized live trio of musicians, literally, a one-man-band.

About MIDI Events

Keep in mind that MIDI information is like a player piano roll; it doesn't contain an actual recording of audio, just a record of all "events".  Once inserted into the player piano machinery,  it makes the keys play, recreating a performance.  A typical MIDI message might "set channel 1 to harpsichord and play the third D note for 2 seconds".
Some common MIDI events are :

• "note on"
• "note off"
• "volume"
• "pitch bend" (usually controlled with a little wheel to the left of the keyboard)
• "instrument patch #" (piano, tuba, drums...)
• "keyboard key #" (C3 is "middle C")
• "channel #" (normally 16 Channels or less; one for each keyboard or module)
• "velocity" (how hard did the key get hit)  

The information transmitted is NOT the actual audio that a synthesizer keyboard sends to the amplifier and speakers.  It is only the actions performed plus current settings.  When a key is pressed, the MIDI information is sent.  If a "MIDI clock" is turned on and transmitted, then the MIDI information can be recorded and saved as a specially compiled text file (normally with the extension, ".mid").  In digital audio software programs with a "MIDI event editor" it looks something like this:

In the event list above, you can see that the Instrument #s and Volumes were set for each track at time "00:00:00:00" and one "middle C" piano note was "triggered".  Track 3 was set to the special Channel 10, which is  normally  reserved for drum sounds.  The piano note was turned off at  "00:00:00:30".  After that, you can see a few more note events for trumpet and piano, and the bass drum and snare drum alternating at the end, with a louder "145" velocity hit on the snare at the very end.  

Up to 16 Channels can be used, with corresponding Tracks for different Instruments.  A Track can be thought of as one player's performance (multiple notes are okay) on a particular Instrument.  Track and Channel (and Instrument) assignments can easily be altered at any time, but it is good practice (less chance of MIDI logjam or hiccups) to keep 1 Instrument on 1 Track on 1 Channel. 

Connecting a MIDI Keyboard to Your Computer

First, you'll need a MIDI keyboard.  These are available at music instrument shops, on the internet, and sometimes in department stores.  If you're looking for an inexpensive keyboard to get started, try a Casio or Yamaha (make sure it has MIDI In and MIDI Out ports on the back panel) from Toys R Us; you should be able to get one for around $150 or less.  High quality MIDI synthesizer/keyboards with great sounds, velocity-sensitivity (transmits how hard you hit each key), weighted (like a real piano) keys, and other features can go for about $1,000 and up. You need two 5-pin MIDI cords to connect to the MIDI In and MIDI Out connectors of your keyboard.

Now you need a MIDI In and a MIDI Out connector on your computer.  Some PCs come equipped, but may need a cord adapter (to connect to "game/MIDI" ports, for example).  Some sound cards, like SoundBlaster Platinum include MIDI ports.  Another solution is to get a MIDI adapter box like "MidiSport"; it plugs into your computer's USB port, and offers 2 or more MIDI connections, depending on the model.  This is a less expensive solution than a new sound card, and works fine on a Mac computer, too.

Using MIDI Software

You'll need a software program to record, edit, and play back your MIDI files.  There are a lot of decent, inexpensive programs (a few free ones) out there; check out the appendix at the end of this article.  
For the Macintosh, you might consider downloading ProTools Free; it's a pro audio and MIDI recorder/editor optimized for the Mac, and it's FREE from Digidesign's website.  PC owners with Windows 98SE or ME operating systems can use it, too.

There are several "high-end" digital audio/MIDI combo programs that are being used to create the hits you hear on the radio.  ProTools is one of them, but the high-end, "non-free" versions of ProTools with custom soundcard runs up to $10,000 and beyond!  Steinberg's Cubase VST (PC and Mac) is as popular, and similar in features, but more reasonably priced; also, if you can show a student I.D., you are eligible for a huge discount at educational software sites (see appendix at the end of this article).  For the PC only, there is Cakewalk's new "Sonar";  it's also reasonably priced, with a very professional set of tools, a moderately easy learning curve, and good manual.  Digital Performer, Emagic Logic Audio, and Nuendo are very popular with big music studios with many complex features like surround sound mixing, and a correspondingly high learning curve.

Once you are connected, you need to make sure that your software is able to "hear" the MIDI input.  On a PC, most programs can utilize the Windows drivers and MIDI controller in the Multimedia/Sounds control panel.  You may need select from the software's MIDI menu to "choose MIDI device", etc.  On the Macintosh, you should install and run Opcode's "OMS" (Open Music System), which helps streamline instrument patching.

Recording MIDI to Your Computer

If you have "MIDI-aware" software, your keyboard is on, and your MIDI connections are connected, then you're ready to lay down a track!   

1. Go to your software's main editing window, pick "Add a New Track" from the File or Edit menu and make sure it's a MIDI, not an "Audio" track.  

2. Most programs have a "Record-enable" button (it may be a tiny red "rec") somewhere on the left of the new Track; push the button.  This is NOT the regular Record button you see on the transport bar below; it's a switch to "enable" recording on a particular Track, leaving other Tracks safe from accidental overwriting.

3. Hit a key on your keyboard while watching the software's "level meters" (you may need to select the level meter from a "Windows" or "Views" menu).  If you see the bars jumping as you play, then you're in business.  If you don't, check to see if your MIDI Track has an input selection; you may need to assign your keyboard to the Track.



4. Find the "metronome" settings (sometimes you can just double-click on the metronome's icon - it's the lit-up blue & white button next to the "2 Bars" button on the Transport Bar above); make sure the metronome is set to "click when recording".  

5. Set the "Tempo"; 120 BPM (Beats Per Minute) or "quarter note=120" is a normal, easy-going "groove".

6. On the "Transport Bar" (the Play, Stop, Rewind, Record buttons, etc.), press the red "Record" button.

7. You'll hear the metronome start to click;  "1, 2, 3, 4,  1, 2, 3, 4..." ("1"s are emphasized).

8. Play to the beat.  

9. When you're done, click the "Stop" button on the Transport Bar.

10. You now have a MIDI Track displayed in the "Edit" Window.

Editing MIDI 

MIDI Editing programs usually offer 3 different display options:
Piano roll	Score/Staff Sheet Notation	Event List

Changes can be made in any view and will show in the other views, subsequently.  Notes can be dragged to different locations, copied and pasted, and all MIDI values can be altered as needed.  MIDI can even be created from scratch within these programs (without a keyboard!) using a pencil tool to draw in new notes and then assigning values.
The Piano Roll view makes it easy to select and modify groups of notes (e.g. snap them to a timegrid-"quantizing" or move them up or down the scale-"transposing").  Some musicians prefer to edit in the Staff Sheet mode, which can also be printed out for live musicians' use. Technically oriented users may enjoy working with the complete data displayed in the Event List view.  It is also useful for tracking down "invisible" events that may be causing problems.

"Sequences" of MIDI tracks can be created and arranged as a "Song".   A "verse" section of 8 measures (8 times of "1, 2, 3, 4") can be copied and pasted into another part of the song.  The second verse might be a copy of the first verse with the trumpet and drum tracks deleted.  Once your song is arranged, it can be saved as a standard MIDI file (extension ".mid").   

Combining MIDI and Audio 

In the high-end digital audio "workstation" programs like Cubase, ProTools, Sonar, etc. it is common practice to begin creation of a piece by laying down MIDI drum tracks, overdubbing other instruments onto more MIDI tracks, and then overdub audio tracks like vocals and "live" instruments.  Sometimes the MIDI instruments are replaced one track at a time by a live performance, adding the human feel of timing imperfections, natural instrument noise, and volume dynamics.  Some processing effects are only available to audio tracks, so a good MIDI track might be routed out and recorded back as audio onto another track, which can then be effects-processed.  The final mix of audio and/or MIDI tracks can be saved as stereo files for audio CDs, movie soundtracks, web delivery, etc.

Good Things About MIDI 

The file size of the MIDI information is very small, especially when compared to the same sounds recorded and saved as digital audio.  If you know the destination system that your music is being sent to has a MIDI player installed, then you can use a MIDI file to cut down web download times and/or system RAM requirements. 

Also, MIDI files, being made of the individual events, can be easily edited, as all of the individual instrument data is still separated.  Contrast this to a "mixed-down" stereo (2 tracks) digital audio ".wav" file.  None of the individual performances within the mixed-down file can be isolated (as MIDI can).  

If you have a computer, you don't even need an instrument to create MIDI music.

One MIDI file may include many tracks of different instruments playing together simultaneously.  You don't need to learn how to play clarinet to create a clarinet performance.

If you're a songwriter, then you can make your own demos with a full band, without having to pay anybody!

Not-So-Good Things About MIDI 

If your MIDI file is played back on a computer or keyboard with cheezy MIDI sounds, your file sounds bad.

MIDI can only trigger the sounds that are in the MIDI library.  That library does not contain your voice, or the sound of screeching tires, or bagpipes (But it DOES have accordian!).  You can't make an entire song that includes vocals and special sounds...yet.

Some "special effects" like "backwards audio" and "wah-wah" are only available for audio files...so far.

If you aren't a musician, it may be difficult to learn but, hey, you're brilliant... it might be fun!

Appendix: Where to find MIDI Stuff 

Here is a list of links that I have found useful:

"Shareware Music Machine" site:     www.hitsquad.com/smm/ .  

Academic discounted software:    www.academicsuperstore.com

ProTools Free download site:    www.digidesign.com/ptfree/

Cakewalk Sonar site:   www.cakewalk.com   

Steinberg Cubase site:   www.steinberg.net

ToysRUs keyboards:    www.toysrus.com   (search for "midi")