(revised 10/04)
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How
Does MIDI Do That?
by Michael Tyler
Computer Music Products
How is it possible for a MIDI music software program to “understand” music? The basic principle is simple -perhaps even brilliant. Every function on a MIDI instrument is assigned a numeric value. When the MIDI Specification was first developed, the unique numbering system it was based upon enabled it to communicate quite nicely with a computer. Computers, of course, are essentially numeric processors. It’s because of this numerical common ground that a MIDI instrument is naturally suited for interfacing with a computer. After all, they are speaking the same language!
When you play a MIDI instrument you hear music. On the other hand, if you connect the instrument to a computer, the computer is “hearing” and recording only the MIDI numbers, not any sound whatsoever. As a matter of fact, you are actually just speed-typing a series of numbers whenever you play your MIDI instrument! I repeat, when you record a MIDI performance, the computer software is capturing only MIDI numbers -no actual sound is being recorded. When you playback a MIDI performance, these numbers are transmitted to your MIDI instrument (or soundcard) and these MIDI numbers “trigger” the sounds that are already built into the instrument. When the built-in sounds are triggered, you hear the playback through the speakers the instrument or soundcard is connected to.
Each note you play on a MIDI instrument has a specific number assigned to it. For instance, if I am using notation software and I play a middle C on the keyboard, the computer recognizes this note as NOTE #60, but I will see the note displayed as standard notation on the computer screen, and I will hear the middle C “triggered” via the attached instrument or soundcard. If I want the computer to change this note one full step up, a +1 number will be added for each half-step interval. In this example, the computer would see the result of this transposition as NOTE #62 (that’s D above middle C to us!).
It’s not only just the notes that have numbers assigned to them. There is a lot more going on than simply entering the notes themselves when you play your MIDI instrument. Each built-in sound on your MIDI keyboard has an INSTRUMENT NUMBER assignment. You select the sound you want by pressing a button on the instrument or by manually entering the instrument number in the appropriate location in your music software. The number assigned to that sound is recorded and saved by the computer, then the MIDI Instrument Number is transmitted back to your instrument during playback in order to permit the note numbers trigger the specific sound you selected.
When you use a sustain pedal, change volume, play expressively (harder or softer), the computer is receiving what are known as MIDI CONTROLLER NUMBERS. When you record MIDI performances, your music software also keeps track of when you play the notes (timing), how fast you are playing (tempo), and how long you hold each note (duration). Again, it can do this because there are specific MIDI numbers assigned to all these events and more. As you play the keyboard, a stream of MIDI numbers are sent in a continuous flow to the computer. Once this information is recorded by your computer music software, the full benefits of MIDI can be realized.
Creative Opportunities
Computer music software has enabled a fascinating opportunity for musicians to be more creative and productive than ever before. For example, a task that many composers face is the transposition of parts for instrumentalists and/or vocalists. This is a task that can be delegated to and accomplished beautifully by a notation software program. By connecting a MIDI keyboard to a computer and selecting the appropriate software, the musician has all the tools necessary to accomplish his or her transposition and notation printing goals. The music can be manually “mouse-click entered” or played from the MIDI keyboard while the computer records the performance. The software displays this on screen as standard notation. Select the key signature you want to end up with, add any musical elements and lyrics, then print out the music in the new key. Once the professional results produced by a notation software program are witnessed and experienced, few musician’s will want to go back to manuscript. The vocalists and instrumentalists highly appreciate the added legibility from a nice printout, too!
Another useful benefit is especially suited for musicians who want to create a special arrangement of an existing song, or compose something entirely original. In fact, musicians who do a lot of composing love MIDI! They can enter each instrument part into their music software, then play all the instrument parts back together through their MIDI instrument to hear how the composition is coming along at any point. Changes made to the score can be aurally “proofread” via the connected MIDI instrument and instantly viewed on a computer screen. Music software makes it exceedingly easy to make changes to your compositions and even print out the new sheet music immediately thereafter. Compare this with the conventional method of writing out all the parts, getting the musicians together, handing out those parts, playing the composition, making corrections, then perhaps changing and rewriting parts -all by hand.
How MIDI Does "The Impossible"
MIDI allows you to perform musical tasks that cannot be accomplished with conventional audio tape recordings. For instance, if you want to speed up the tempo of a song recorded on tape, you have to make the tape itself play faster. But, the disadvantage is that the sound of your music will change -it will go up in pitch. Not exactly desirable unless you do soundtracks for the Chipmunks!
However, if you want to speed up the tempo of a MIDI-recorded song, you just type in any tempo setting you want and the pitch of the music will stay exactly the same. Why? Remember that when you are recording a MIDI performance, you are not recording any sound -you actually record only MIDI numbers. You already know that each note pitch has its own numeric assignment. So when you increase the tempo for MIDI playback, you are just telling the software to send all these numbers back to your attached MIDI instrument at a faster rate. When you play back your performance, the MIDI instrument sounds are “triggered” and you hear the music! All the actual note numbers are still the same. Same number, same pitch. Of course, this works just as well for slowing down the tempo of a song. Neat, huh?
Changing instrumental parts and playback properties in a MIDI recording is a snap. You can freely experiment with different instrument sounds by manually changing the INSTRUMENT NUMBER. If you originally recorded a song with an oboe part, then later wished you had used an English horn instead -just change the instrument number for that part. You do not have to re-record a new part. The song plays back as it was originally recorded, but you now hear the English horn playing the (formally) oboe part!
Change the dynamics of any part by changing VOLUME, EXPRESSION or VELOCITY CONTROLLER NUMBERS. In a MIDI recording software program, there are usually on-screen slider controls, similar to that found on an actual audio mixing board. If you want to fade in or fade out, you just slide the faders and the software takes care of inserting the appropriate numbers for you -automatically. Change your mind, and you can delete these changes at any time. A MIDI instrument coupled with computer software can be a powerful compositional tool in the right hands. Good musicianship prevailing, of course!
The Secret to Authenticity
Lest you think I’m out to convince you that MIDI is a total substitute for conventional instruments -I’m not, and it isn’t. It would be great if every composer had a full compliment of musicians at his beckoning call anytime, day or night. No one that I know of has such an advantage, but with a good quality MIDI instrument and some software, you can sound like you do!
Most of us record our soundtracks using a MIDI keyboard to play our compositions into a MIDI recording program. I think the essential ingredient when using a MIDI keyboard to replicate a non-keyboard instrument (like woodwinds, strings, brass, etc.) is to try to “think like” the musician would when playing the real instrument. You have to be ready to adjust your playing technique according to the instrument sound you have selected.
For instance, when playing a stringed instrument sound via your keyboard, try think like and play like a string player. The result of a conscious effort to mimic various instrumental techniques will be a much more effective and realistic soundtrack to the ears of the listener. Here’s another example. Although I have never actually played a real oboe myself, I do know how an oboe is supposed to sound. I do my best to add the subtle nuances that will make a “MIDI oboe” feel and sound authentic. When appropriate, I will often use the pitch/modulation lever on my synthesizer keyboard to add slight pitch bends and vibrato while playing woodwind, brass and string sounds. All this serves to refine the illusion that the “real” instruments were used to perform the various parts.
It can be very useful to listen to tapes or CD’s that feature the instruments you plan to “play” on your MIDI keyboard. Study how they sound, listen how each musician uses expression and dynamics through his or her instrument, then apply what you have learned to your keyboard playing technique. There is just no substitute for good musicianship and thoughtful practice.
Conclusion
I hope this article has helped you understand a bit of the inner workings of MIDI. By taking advantage of the latest music software programs, you can have a great deal of fun while expanding your musical capabilities well beyond what you may have previously thought was possible!
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