First of all, Ondas Tropicais is Tropical Waves in Portuguese – and Portuguese is a language much spoken in tropical zones due to colonial history. Brazil in Latin America; Angola, Guine-Bissau, Cabo Verde, São Tomé e Principe in tropical Africa; East Timor and Goa in tropical Asia. And I love the music from many of these places, especially Brazil and the African countries mentioned. Sound waves.

Then there is a natural electromagnetic phenomenon which produces tropical waves that spread all round planet earth, called the Schumann Resonance.

Think of it as if the cavity between the earth and the layer of charged particles called the ionosphere, at 100+ Km above the surface functions like a giant electromagnetic drum. So, in the same way that an acoustic drum has resonant frequencies depending on its size this cavity does for electromagnetic waves. If one wave fits into this spherical cavity that is approximately 40,000 Km long, that distance will be the wavelength of the lowest possible resonance. And as for all waves their frequency is calculated by dividing their propagation speed by their wavelength. The speed of light and therefore of all electromagnetic radiation is 300,000 Km/sec, so our calculation produces the wavelength of 7.5 cycles/sec or Hz, and this frequency happens to be close to that of the human brain’s Alpha-rhythm…

There is just one thing missing in this model - who is the drummer?

And this is where the Tropical connection arises.

Thunderstorms are occurring across the whole band of tropical latitudes every day, usually in the local afternoon, and these bursts of electromagnetic energy are the drumbeats of the earth-ionosphere cavity, each setting off a range of the frequencies shown in the figure on the left.