Article by: Terry Wilhite

Elsewhere we’ve talked about what I call the MIDI chain – the components that have to be present and working for your synthesizer and computer to communicate. This time we’ll continue our discussion by clarifying some terms. Whether you’ve used MIDI for a while or you’re new to it, coming to terms with this technology can help you greatly.

MIDI OUT
For the record, MIDI does not transmit sound. When you play your keyboard, the computer inside your synthesizer transforms what you play into digital information via MIDI – Musical Instrument Digital Interface – pronounced MID-ee.

For your computer and digital instruments to communicate, simply remember, when your computer and synthesizer are connected properly, the IN plug goes into the OUT port and the OUT plug goes into the IN port. That’s all there is to connecting a basic MIDI set up! Typically now, in a basic set up, a simple MIDI interface box allows MIDI connections on one side and a USB connection on the other, which goes to your computer or digital audio workstation. Some keyboards now even have a USB MIDI connection so no interface is needed at all. Very nice.

MIDI IN
When you play a MIDI file using software such as Cubase on your computer, MIDI drivers send the signals from your soundcard into the MIDI IN of your synthesizer. The synthesizer then plays the data just as if you were pressing the keys yourself. If your MIDI instrument is not responding to all the MIDI commands that are being sent, your keyboard may have been pre-set by the manufacturer to filter certain MIDI commands. Bank change information, for example, may be filtered, meaning your synthesizer won’t know to change sounds if a MIDI file you’re playing tells it to do so. Grab your synthesizer’s instruction manual. It should tell you how to disable these filters so that all incoming MIDI information can be received. You will want your keyboard to receive and respond to all MIDI data.

MIDI THRU
Anything that goes into the MIDI IN port will transmit from the MIDI THRU port. Think of MIDI THRU as simply a repeater. Why would you need such? You can chain MIDI instruments! You can have an “orchestra” of MIDI instruments – a synthesizer, a drum machine, a rack mount unit, that is a synthesizer without a keyboard. In other words, you can play one keyboard and have sound come simultaneously from other instruments. If you want to send MIDI signals from your computer to two synthesizers, connect your computer and keyboard just the way we’ve explained. To connect the second keyboard, all you would have to do is to run another cable from the MIDI THRU from the first keyboard to the IN port of the second. If you connect your MIDI system this way, your computer will be able to send instructions to both synthesizers. However, you will not be able to play the keyboard of synthesizer number one and have synthesizer number two respond. Remember what you play on your keyboard only goes out of the MIDI OUT, not the MIDI THRU! If you play the first synthesizer and have the instruments on synthesizer number two sound, you will need a MIDI interface box – basically a splitter – which has two or more inputs and usually four or more outputs. Some interfaces even include software so you can tell MIDI instruments when to respond to transmissions using an on-screen set up window on your computer. If you have multiple MIDI instruments and use an interface, you’ll want to choose your master MIDI instruments – say your computer and your first synthesizer – and run a MIDI cable from each of those devices into the IN ports of the MIDI interface box. Then you’ll run one MIDI cable from each OUT of the interface into the IN of each MIDI instrument.

MIDI CHANNELS
You can hook all of these keyboards up and have each to play what you want them to by using MIDI channels. Just as you tune to a certain television channel to see what you want to see, with MIDI, you set your synthesizer to receive the signals that are being transmitted from the source that is originating them. Usually, as long as your synthesizer is in the mode that allows multiple instruments to play at once – called the multi timbral mode – your synthesizer will automatically receive the various instruments that are being sent via the 16 MIDI channels. Synthesizers differ. You’ll need to take a peek at your instruction manual to see how yours handles MIDI and if it can play multiple sounds at once. Let’s say that you’re playing a MIDI file on your computer and want two synthesizers to play the music. We’ll set our software up to transmit an acoustic piano on channel 2, guitar on channel 3, strings on channel 4 and drums on channel 10. Then we’ll set synthesizer number one to receive channel 2 and channel 3, the piano and guitar. We’ll set the second synthesizer up to receive channel 4 and 10 so that it plays the strings and drums. If a trumpet sound is accidentally set on Channel 2 on either keyboard, it’s going to play the notes meant for the acoustic piano! Remember we’re only addressing MIDI here. To mix sound sources, you’ll need an audio mixer.

SYSTEM EXCLUSIVE MESSAGES
While MIDI is a common digital instrument language, each synthesizer speaks a “regional dialect” that contains information exclusive to its maker. This data is contained in a System Exclusive Message – SysEx for short. Often MIDI files that you buy will send SysEx information to your keyboard to take full advantage of the features of your keyboard. Librarian and editor software that allows you to tweak and store your synthesizer’s sounds on your computer uses SysEx.

ACCESSING HIGHER BANKS
If you want to transmit MIDI data to instruments on higher synthesizer banks – Banks B or C, for instance, you will have to tell the computer software how to access those banks. Some software will ask you for MSB (Most Significant Byte) and LSB (Least Significant Byte) numbers. Find out these numbers from the instruction manual or your dealer, simply enter them in the software, press the enter key and the synthesizer should respond.