Software Synthesizers (Excerpt): Top Music Technology Pages Return to MusicWords Home

[The material below is excerpted from Software Synthesizers, published in 2003 by Backbeat Books.]

Playing a software synthesizer from your computer's QWERTY keyboard is possible (depending on the software), but not much fun, except for testing the software or goofing around. Most softsynths are played using MIDI keyboards.

Some MIDI keyboards attach directly to the computer with a USB cable. Older ones may use a serial or parallel cable. If your keyboard isn't equipped with one of these connectors, you'll need to attach a MIDI interface to your computer, and connect the keyboard's MIDI out jack to the computer's MIDI in jack using a MIDI cable.

MIDI (the Musical Instrument Digital Interface) is a communications standard used for transmitting musical performance information. Whole books have been written about MIDI. Fortunately, you can get up and running with software synthesis without worrying too much about the details. Here's what you need to know:

When you press a key on a MIDI keyboard, the keyboard sends out a message containing four essential items of information. First, it contains a few bits identifying it as a type of message called a note-on, which tells any receiving device that a note has just started. Second, the message contains a channel number. MIDI defines 16 different channels, all of which can be active on the same cable at the same time. Third, the message contains a note number, which tells the receiving device which note was played. Finally, the message contains a velocity value, which indicates how quickly the key was moving when it struck the keybed.

When you lift your finger from the keyboard, more or less the same thing happens: The keyboard transmits a note-off message, which contains a channel number, a key number, and a note-off velocity. (The note-off velocity value is rarely used.)

It's important to understand that MIDI note-on and note-off messages contain no information about the actual sound that you'll hear. If the synth on the receiving end is set to make a flute sound, that's what it will do. If it's set to make a drum sound, a drum sound is what you'll get. The transmitting keyboard neither knows nor cares what happens after it sends the note-on. The receiving synth could even be switched off or malfunctioning. That makes no difference to the keyboard, because MIDI -- unlike, for example, the data flying back and forth in a printer cable -- is a one-directional protocol. If the printer is out of paper, it can let your computer know. MIDI isn't quite that sophisticated.

An even more basic point that's sometimes misunderstood by folks who are just getting started: Because MIDI cables can't carry actual sounds, you can't record the sound coming from an external hardware synthesizer into your recorder software by connecting the synth to the computer via MIDI. All you can do with MIDI is record and play back performance information. To record any sound into the computer, you have to use its audio I/O facilities, whatever they may be.

Your keyboard will probably contain other types of performance controllers -- pitchbend and modulation wheels, for instance, or knobs and sliders on the front panel. Each of these will send its own type of MIDI message. But here again, it's up to the receiving synthesizer what to do with the messages. It may even ignore them entirely.

Most of the software synths discussed in these pages can respond to MIDI controller data in various ways. Some can also generate controller data from their on-screen knobs and sliders. Assuming the synth is operating as a plug-in, you may be able to record this data into the host sequencer. MIDI controllers are an unbeatable way to make your synthesizer performances sound more interesting and expressive.