A driven coupled system shows two separate resonance peaks

Evidence

When one of the two pendula is driven, either pure sinusoidal mode can be excited, if the driving frequency is resonant. This is seen in figure 10.8, which reveals two resonance peaks reached as the left pendulum is driven sinusoidally over a range of frequencies. — Eric J. Heller, Why You Hear What You Hear- An…, 1028