On an oscilloscope, tremolo will always show up as a periodic change in amplitude. Vibrato, on the other hand, will show up as a periodic change in either wavelength or phase.

The amplitude is the height of the wave.

The wavelength is the distance from one wave top, or crest, to the next.

The phase shift describes how far to the left or right the wave slides.

Move the sliders back and forth in the demonstration to the left. Notice how changing their values affects the shape of the wave drawing.

To see and run this application the Java Runtime Environment needs to be downloaded and installed first.