Two strings are stretched side by side: one thick and dull, the other thin and bright. Pluck the thick one, and you get a muddy sound with no clear pitch. The thin one responds with a pure tone. But link them together, and an unexpected effect appears: a sharp dip in the spectrum, as if someone muted a single note. This is the Fano resonance — a phenomenon physicists know from atoms, light, and even radio waves.

Now it has been reproduced in a miniature mechanical system. A sheet of graphene, just one atom thick, was placed on a tiny silicon nitride plate. The graphene vibrates sluggishly and broadly, like a big drum, while the silicon nitride sings with many narrow, high-pitched tones, like a comb with fine teeth. When the drum and the comb vibrate together, their voices interfere: at some frequencies they amplify each other, at others they cancel. By adjusting the gate voltage, you can shift these frequencies relative to each other and thereby switch the Fano resonance: change its sign and strength.

A weak additional tone can flip the system from one step to the next. This is like shifting gears in a transmission: each position is fixed and independent of how hard you press the pedal. This 'frequency ruler' made of silicon nitride stabilizes the graphene's vibrations, turning the hybrid device into a precise mechanical frequency standard.

The practical benefits are clear: mass and force sensors become more sensitive, and clock generators become more stable. Instead of complex electronics to fine-tune the frequency, you just apply a DC voltage. Two strings coupled on a single chip give more than either alone.