It was an unusual Saturday, last 21st September for visitors of Vesuvius. Once they came back from the top of the Volcano at the altitude of 1000 meters, they found an INGV geophysicist, Vincenzo Sapia, displaying instruments to acquire “notes” from the Volcano. The notes were used in the next hours to start a jazz improvisation by the Jazz Quartet leaded by Marco Guidolotti, a renown Italian saxophonist. The other components, the guitar player Stefano Pontani (artistic manager of the project EMusic, ElectroMagnetic Music), Valerio Vantaggio at the drums, Francesco Pierotti at the contrabass, and Felice Tazzini at the piano.
But how can we extract “notes” from a Volcano? Sapia explained to the visitors how geophysicists acquire data from the soil using an antenna, after having excited the ground by creating an electromagnetic field by inducing an electric current. When the current is suddenly interrupted a secondary magnetic field is created and the signal propagate under the soil. How the soil respond to the current is the data acquired, and the data depends on the nature of the soil. If the soil is conductive, the response will be slow, while if the soil is resistent the response will fade away quickly becoming difficult to capture. This was the case of he Saturday 21 sept concert area. Sapia was in fact taking data from the lava produced in the last Vesuvius’ eruption in 1944. Instead, the more is the soil conductive the more data can be acquired and transformed into notes.
What kind of music could visitors expect in this case? Geophysicist Antonio Menghini (scientific manager and initiator of the Emusic project) explained how the signals coming from the ground is transformed into notes. The data collected consist of voltage values tending to decrease over the time traveling deeper into the soil. “The idea I had with S. Pontani – explained Menghini – was to transform these voltage values into audible frequencies. As the signals tend to fade, if we arrange them in a music pentagram we will have notes gradually lower in tone. So, what you will hear during the concert will be the higher notes first because coming from the more superficial layers. Gradually they become lower and lower because they derive from deeper layers. The voltage variation comes from the type of rock we have below us, so, the pentagram shape, when we put it on a graph, will give us a different sequence of notes from site to site. For example, here we expect to find lavas and scoriae that barely conduct electricity, so we will not be surprised if the signal fade immediately. This means that within a pentagram the notes we take will be very distant from each other. The opposite case may be instead the case in which the ground conducts the electric current much better, allowing the signal to remain high. In this case in the pentagram you will have notes closer, therefore a chromatism”. (to learn more see the video)
The visitors experienced both the cases since the data used were also those acquired some days before in another site of Vesuvius, where the lava dated back to the Pompei eruption of 79 AD. Believe it, the lava that destroyed Pompei is more conductive and the tones of the second part of the concert higher. Have a look at the video we prepared for you.
The event was organized by the City of Naples, the Geological Survey of the Campania Disctrict, The National Park of Vesusvius , E-Music and INGV Rome.