New in version 2.0.
Calculate harmonic diatonic interval-class from pitch_carrier_1 to pitch_carrier_2:
abjad> pitchtools.calculate_harmonic_diatonic_interval_class_from_named_chromatic_pitch_to_named_chromatic_pitch(pitchtools.NamedChromaticPitch(-2), pitchtools.NamedChromaticPitch(12))
HarmonicDiatonicIntervalClass('M2')
Return harmonic diatonic interval-class.