A sum of sinusoids takes the period of the slowest common component

Evidence

The waveform resulting from the addition is now a complex signal, or musically a complex tone. It has a frequency of 220 Hz (it repeats every T = 1/220 seconds, but not sooner), even though 440 Hz is present. The 440 Hz sinusoid repeats twice as often as a 220 Hz sinusoid. — Eric J. Heller, Why You Hear What You Hear- An…, 340

Categorization

• DEFINE: Defines complex tone and the fundamental-period rule for sums of partials.
• XREF: Connects to concept of the fundamental as pitch perception basis — relevant to how the ear hears a missing fundamental.