key_type(white).
key_type(black).
key_color(c, white).
next_white_key(c, d).
next_white_key(d, e).
next_white_key(e, f).
next_white_key(f, g).
next_white_key(g, a).
next_white_key(a, b).
next_white_key(b, c).
semitone_gap(e, f, 1).
semitone_gap(b, c, 1).
semitone_gap(X, Y, 2) :-
next_white_key(X, Y),
X \= e,
X \= b.
has_black_key_between(X, Y) :-
next_white_key(X, Y),
semitone_gap(X, Y, 2).
octave_size(12).
total_keys(88).
style(jazz) :-
wrong_notes > 0,
write('All wrong notes are now intentional').
Just a joke on what makes a piano, i suppose the pun is intended but Peano’s axiom are famous mathematical axioms.