“The big brother of ultrasound, infrasound means frequencies too low to be heard by the human ear. Infrasound occurs naturally – from waves pounding shores, storms, earthquakes, meteors hitting the atmosphere. Longer pipes in church organs also create infrasound, which many believe gives the music a particular atmospheric power. Humans have a hearing range of roughly 20 to 20,000 Hz (the lowest note on a piano is around 33Hz). Sounds that fall below that threshold are not audible – but they are felt.” And musicians are learning to play with it.