The Universe began with a rapid inflation — expansion of the universe. Almost the whole piece was led by one field, the inflaton. But towards the finale, charged fields might have briefly awoken, and their appearance would have changed the 'sound'. Gravitational waves, like a sensitive microphone, would have recorded this shift. While a field is calm, it hardly generates any ripple. But once it gets excited, space begins to oscillate at very high frequencies.

What exactly gives away the charged fields? Sharp modulations appear in the wave spectrum. Two key numbers, the charge strength and the field energy, make the main peak jump from place to place. With neutral fields, the peak shifts smoothly, like the hand of a clock. But here it's a leap, as if the minute hand jumps ahead ten minutes. This contrast is the telltale sign.

Catching such a signal is a task for future detectors. They will work like microscopic radio receivers, tuned to waves a few centimeters long. If the instruments pick up the characteristic peak jump, it will confirm that an electric solo truly sounded in the Universe's infancy.