AESH/Esha on Instagram: "Beat Frequency Oscillators were built in the 1950s by companies like Brüel & Kjær, not for music, but for precision. They were designed to test rooms, speakers, microphones, and even the limits of human hearing. Pure measurement tools. Clinical. Exact. And yet, experimental composers saw possibility. A BFO generates two nearly identical frequencies. When they interact, the ear doesn’t hear them separately. It hears the difference between them. A wobble. A beat. A pulse.