+enum
+{
+ DOUBLE_FLAT = -4,
+ THREE_Q_FLAT,
+ FLAT,
+ SEMI_FLAT,
+ NATURAL,
+ SEMI_SHARP,
+ SHARP,
+ THREE_Q_SHARP,
+ DOUBLE_SHARP,
+};
+
+extern Rational DOUBLE_FLAT_ALTERATION;
+extern Rational THREE_Q_FLAT_ALTERATION;
+extern Rational FLAT_ALTERATION;
+extern Rational SEMI_FLAT_ALTERATION;
+extern Rational NATURAL_ALTERATION;
+extern Rational SEMI_SHARP_ALTERATION;
+extern Rational SHARP_ALTERATION;
+extern Rational THREE_Q_SHARP_ALTERATION;
+extern Rational DOUBLE_SHARP_ALTERATION;
+
+SCM ly_pitch_diff (SCM pitch, SCM root);