Wave Upon Wave II graphically illustrates the basics of wave combination. A two wheeled axle rides on two tracks that are shaped as waveforms. The rear track has a wavelength of 6 inches, with a 1.5" amplitude. The front track can be selected with either a similar waveform, or second harmonic, or third harmonic, each with an inverse proportion in amplitude. As the axle is pulled along the wave crests, the waves are summed together and a trace along a phosphor screen is recorded. The rear track can be moved to change the phase of the waves. The combination of tracks can be used as a simple Fourier synthesizer to create a sinewave, and roughly create square, sawtooth, and triangle waveforms.