Introduction to MIDI and Computer Music: Local Control

Understanding Local Control

Any MIDI keyboard has an internal sound generator — the circuitry that makes the sounds you hear. (Some MIDI synths have a sound generator without a keyboard.) When recording with an external sequencer, like Digital Performer, you must disconnect the Korg keyboard from its internal sound generator. Why? Because if you don't, you might hear a different sound than the one you want.

Here's what happens. When you play a note on the keyboard, a MIDI note-on message travels to the computer sequencer (over a MIDI cable). The sequencer immediately sends the note-on message back to the keyboard's sound generator, which plays an appropriate sound. What if the keyboard is connected internally to its sound generator? Then one note will play in direct response to the key press — without travelling through the MIDI cable — and another note will play in response to the note-on message returning from the sequencer.

Depending on sequencer and keyboard settings, these two notes will have the same sound, but doubled, or they'll have two different sounds. So you hear two notes, one of them unintended. The solution is to keep the sound generator from responding directly to the keyboard, and have it respond only to MIDI messages returning from the sequencer.

The term re-channelize in the graphic above refers to a feature of the sequencer. When the sequencer "echoes" back the MIDI messages it receives from the keyboard, it can change the MIDI channel number of those messages. This is done so that you can transmit on one channel from the keyboard and use the sequencer to switch the channel that receives those messages, thereby letting you quickly switch between the various sounds you're using. In Digital Performer, you do this by record-enabling tracks that are set to different channel numbers.

The nature of the connection between a keyboard and its internal sound generator is referred to as local control. To disconnect a keyboard from its sound generator, turn the local control setting to off. You should do this any time you're working with Digital Performer. Turn local control on again when you're using the synth without a computer sequencer running.

Setting Local Control on the Korg

Here's how to change the local control setting on the Triton Le.

Press the GLOBAL mode button.
Press the MENU button.
Press function key F2, which is beneath the MIDI item on the page menu.
Press F8 (the Open function key). Now you should see a screen like the following.
Using the arrow keys, navigate to the checkbox labeled "Local Control On."
Use the INC or DEC buttons to check or uncheck the setting.

NOTE: Please turn on local control when you're done recording, or else the keyboard will not sound for the next user.