Separate a MIDI keyboard from its sound generator
If your MIDI keyboard has an internal sound source, it’s important that you stop the keyboard from generating sounds directly from its own keyboard.
For example, if you buy a new keyboard to be used without a sequencer, and connect it to an amplifier, you would expect the device to make a sound when you press its keys—in other words, the keyboard is directly connected to the sound generator.
When using the MIDI keyboard with Logic Pro, however, this is not what you want to happen. In this situation, the keyboard is used as a computer input device, and Logic Pro passes the incoming performance information back to the keyboard’s sound generator (or to an internal software instrument or another connected sound module, if you like).
If the direct connection between the keyboard and its tone generator isn’t cut, a doubling of each note results—one played directly from the keyboard to the internal tone generator, and another sent through Logic Pro back to the tone generator.
Not only does this cause a phased sound, but it also halves the polyphony of the keyboard’s tone generator. In situations where you want to control or record another sound module or software instrument with your keyboard, you would hear both the keyboard sound (due to the direct keyboard–to–tone generator connection) and the sound of the software or MIDI instrument. This is why the keyboard must be separated from its own internal sound generator.
This function is known as Local Off, and is set directly on your keyboard. Don’t worry about losing the ability to use the tone generator of your keyboard. Logic Pro will still be able to communicate with your keyboard tone generator just like any other connected, keyboardless sound module or software instrument.
Note: If you can't find the Local Off function in the MIDI menu of your keyboard, check its manual on sequencer use. Some keyboards allow you to select from Local, MIDI, or Both for each of their Parts (individual MIDI channels/sounds in multi-timbral MIDI devices). The MIDI setting, if applicable to your keyboard, is the equivalent of Local Off.