VCA.MUS.2

Lesson Summary 

Analyze tremolo in popular music.

History 

Listen to historically significant musical examples of the Moog and VCA modulation as well as tremolo. 

 

 Figure 1. The Beatles experimenting with an early Moog synthesizer.

 
Vocabulary 

Amplifier - An electronic device that increases the power of a signal by taking energy from a power supply and increasing an input signals amplitude.

VCA -  An amplifier whose gain is set by the voltage level of a control signal.

Tremolo - A musical effect made by varying an instruments amplitude. 

Gain - The ratio between the magnitude of output and input signals.

Exercise 

Observe a tremolo effect in the Werkstatt.

Materials 

1 x 10kΩ Potentiometer

Jumper Cables

Hardware 

First we need to match our Werkstatt settings to Figure 1. 

 

 Figure 1. VCA Modulation setting

 

By connecting the LFO OUT to our 10kΩ potentiometer we have a level of control over how much modulation is sent to our VCA.  

 

  Figure 2. LFO through 10kΩ potentiometer.

Software 

To see what this VCA modulation looks like we will need to plug our Werkstatt's audio output into an audio input on whatever computer we are using.  On my laptop I am simply changing the headphone output settings to allow the port to act as an input.  

 

 

 

Once we are sending signal into our computer we need to check that it is the primary audio input source.  If the Werkstatt is plugged into the primary audio input source then we are ready to run our Audio_In.pde program. Audio_In.pde also allows the user to increase the visual amplitude of the incoming audio as well as pause the wave animation.  These can be controlled by pressing the arrow keys. 

↑  Amplitude Increase

↓  Amplitude Decrease

←  Pause Animation

→   Play Animation

For more information refer to the comments in Figure 3.

 

  Figure 3. Screen capture

 

Once we run Audio_In.pde slowly turn the 10kΩ potentiometer to send more of the LFO modulation voltage to the VCA.  We should see something similar to the animation in Figure 4. Experiment with various LFO rates and modulation voltage mix levels and observe the wave shapes created. 

 

 Figure 4. VCA modulated wave.

Downloads 

Processing is an open source programming environment and community.

moog_werkstatt processing_files.zip

 

Subject 
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