New in version 2.0.
Calculate melodic diatonic interval-class from pitch_carrier_1 to pitch_carrier_2:
abjad> pitchtools.calculate_melodic_diatonic_interval_class_from_named_chromatic_pitch_to_named_chromatic_pitch(pitchtools.NamedChromaticPitch(-2), pitchtools.NamedChromaticPitch(12))
MelodicDiatonicIntervalClass('+M2')
Return melodic diatonic interval-class.