These are holographies taken in ENEA laboratories in the following way:
Trigger >electromagnet pulse >release of a teflon weight from a predetermined distance> weight contact with a rotating lever which enables the plectrum to pluck the string > two photograms taken in refracted laser light in a sequence of a millionth of second one from the other, after a predetermined half a second, one second, one second and a half, two seconds and a half, four seconds lapse.
comparison between "Greci" guitar and Ramirez 1st class guitar