/**
Counter=5

?- chorussoloprogression('F','G').

[[F, G], [F, A#, C, D, G]]

Yes

?- chorussoloprogression('E','G').

[[E, A, D, G]]

Yes

?- chorussoloprogression('G','C').

[[G, C]]

Yes

**/

chorussoloprogression(Name1, Name2) :-
	note(Note1, Name1),
	note(Note2, Name2),
	chorussoloprogression1(Note1, Note2, 0, _, [Note1], Progression1), notestonames(Progression1,Progression2), writeln(Progression2).
chorussoloprogression1(_, _, _, Counter, b, Progression, Progression) :-  
	Counter = 8, !.
chorussoloprogression1(Note, Note, _, _Counter, a, Progression, Progression) :- !.
chorussoloprogression1(Note1, Note2, Counter1, Flag1, Progression1, Progression2) :-
	Counter2 is Counter1 + 1,
	step1(Note1, Note3),
	append(Progression1, [Note3], Progression3),
	chorussoloprogression2(Note3, Note2, Note1, Counter2, Flag2, Progression3, Progression4),
	step2(Note1, Note4),
        append(Progression1, [Note4], Progression5),
        chorussoloprogression2(Note4, Note2, Note1, Counter2, Flag3, Progression5, Progression6),
	flag1([[Flag2, Progression4], [Flag3, Progression6]], Flag1, Progression2).
chorussoloprogression2(_, _, _, Counter, b, Progression, Progression) :-
        Counter = 8, !.
chorussoloprogression2(Note, _, Note, _, _, _, _) :- !.
chorussoloprogression2(Note, Note, _, _Counter, a, Progression, Progression) :- !.
chorussoloprogression2(Note1, Note2, Note3, Counter1, Flag1, Progression1, Progression2) :-
        Counter2 is Counter1 + 1,
        step1(Note1, Note4),
        append(Progression1, [Note4], Progression3),
        chorussoloprogression2(Note4, Note2, Note3, Counter2, Flag2, Progression3, Progression4),
        step2(Note1, Note5),
        append(Progression1, [Note5], Progression5),
        chorussoloprogression2(Note5, Note2, Note3, Counter2, Flag3, Progression5, Progression6),
        flag1([[Flag2, Progression4], [Flag3, Progression6]], Flag1, Progression2).
step1(Note1, Note2) :-
	Value is Note1+2, Note2 is Value mod 12.
step2(Note1, Note2) :-
        Value is Note1+5, Note2 is Value mod 12.
notestonames(Progression1, Progression2) :-
        clean(Progression1, Progression2).
flag1(Items, Flag, Progression) :-
        flag2(Items, Flag, [], Progression), !.
flag1([], b, []) :- !.
flag2([], a, Progression, Progression) :- !.
flag2([[a,Progression1]|Items], _, Progression2, Progression3) :-
        append(Progression2, [Progression1], Progression4),
        flag2(Items, _, Progression4, Progression3).
flag2([[b,_]|Items], _, Progression2, Progression3) :-
        flag2(Items, _, Progression2, Progression3).
clean(Items1, Items2) :-
        clean1(Items1,[],Items2).
clean1([],I,I).
clean1(Items,I1,F1) :-
        allnumbers(Items,[],Names),append(I1,[Names],F1),!.
clean1([Item|Items],I1,F1) :-
        clean1(Item, I1, F2),
        clean1(Items, F2, F1).
allnumbers([],Names,Names).
allnumbers([Item|Items],Names1,Names2):-
        number(Item),note(Item,Name),append(Names1,[Name],Names3),allnumbers(Items,Names3,Names2).
note(0,'C').
note(1,'C#').
note(2,'D').
note(3,'D#').
note(4,'E').
note(5,'F').
note(6,'F#').
note(7,'G').
note(8,'G#').
note(9,'A').
note(10,'A#').
note(11,'B').