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Local Control
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Fall 2005
Due to a partial redesign of the course and introduction of both new course content and new software, some of the old syllabus chapters have been removed from the web site. Updated material will be posted in the future.
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Local Control is a parameter that you can set on your sythesizer or other MIDI device. Local control may be turned on or off using controls on the device. By default, local control is normally on when you switch on the power to your synthesizer. This default setting is appropriate if you are playing the keyboard directly rather than using it in a MIDI sequencing environment. However, leaving local control on when using a synthesizer as a controller along with sequencing software may create problems. For example, you may press a key to hear a piano sound and hear another sound playing along with the piano on the same pitch.
Incorrect local control settings are a frequent cause of problems in the studio. The most common error is caused by leaving local control on when working with sequencing software. This can cause parts to be doubled in error and can cut the number of available polyphonic notes in half.
How Local Control Works
To understand how local control works, think of a synthesizer as being composed of two separate, linked parts, the controller and the tone generators. The controller is the part of the instrument that the player interacts with, for example the keyboard. The tone generators are the internal circuitry that generate the signals which ultimately emerge from loudspeakers as sound. With local control turned on, interacting with the controller (in plain english "hitting some keys!") sends messages to the tone generators, causing them to produce audio signals. This is, of course, exactly what you want to have happen in most situations.
With Local Control turned off, the instrument's tone generators will not respond to its keyboard (or other controller). There is no particular advantage in using this setting when operating a "stand-alone" synthesizer, since it makes the instrument essentially non-functional. However, there are good reasons to turn local control off when controlling an instrument from a sequencer, or when using the keyboard as a controller with other instruments.
It is common to set up a sequencer so that MIDI input from the controller keyboard is immediately "echoed" back out of the sequencer. (This feature is sometimes known as "MIDI THRU.") When the sequencer receives a MIDI event - such as a note on message - it immediately sends it back out the MIDI out port to the synthesizer(s). However, if the synthesizer's Local Control is also left on, the synthesizer will receive two notes every time one key is pressed. One will come directly from the local keyboard through the internal circuitry of the instrument, and the other will come by way of the sequencer, arriving at the MIDI in port. In many cases, the effect is not immediately audible, since the two notes may be identical and therefore indistinguishable. However, if the synthesizer produces two tones each time one key is pressed, its maximum polyphony (number of notes it can play at one time) will be cut in half. When Local Control is turned off, the synthesizer will not receive a "note on" message directly from its local keyboard, but will still receive one from the sequencer (in most cases) via the MIDI interconnections. The following illustrations shows the path a Note On message will follow in this case.
Changing the Local Control Setting
The local control setting is changed directly on your controller synthesizer. The actual steps to change the setting vary by manufacturer and instrument model. In general, you must find a setting called Local Control or "local" and set it to either "on" or "off." You may need to read your instrument's manual to determine how to do this.
You can change the local control setting on the Roland XP-10 in the studio by following the procedure described below. You will need to do this any time the syntheizer's power has been turned off or if the previous user did not turn local control off.
- Press the EDIT button on the synthesizer.
- Find the "+" and "-" VALUE buttons and use them to change the display to read System Setup.
- Press button 7.
- Look at the display. You should see the word "LOCAL" and, to the right, the word "ON." Press the "-" VALUE button to change the display to read "OFF."
- Press the EDIT button again to exit the edit mode.
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