New in version 2.5.
True when expr is a pitch-class / octave number string. Otherwise false:
abjad> pitchtools.is_pitch_class_octave_number_string('C#2')
True
Quartertone accidentals are supported.
The regex ^([A-G])([#]{1,2}|[b]{1,2}|[#]?[+]|[b]?[~]|)([-]?[0-9]+)$ underlies this predicate.
Return boolean.