Although Lissajous figures are familiar to undergraduate physics students, they are usually observed as steady-state figures on an oscilloscope. Our approach produces these figures by modulating the trajectory of a laser beam by two independent mechanical oscillators tuning forks, showing that the concept of Lissajous figures is very general. An interesting question is how similar are the frequencies of otherwise identically tuning forks. Our experiments provide a way to determine differences as small as 0.01 Hz.