for MS being non empty satisfying_Real satisfying_equiv satisfying_interval satisfying_commutativity satisfying_Nat satisfying_harmonic_closed satisfying_fifth_constructible classical_fifth satisfying_octave_constructible classical_octave satisfying_octave_descendent_constructible MusicStruct
for fondamentale being Element of MS holds (spiral_of_fifths (MS,fondamentale,fondamentale)) . 5 = (243 / 128) * (@ fondamentale)