New in version 2.5.
Change default_instrument_name to class name:
abjad> instrumenttools.default_instrument_name_to_instrument_class('clarinet in E-flat')
<class 'abjad.tools.instrumenttools.EFlatClarinet.EFlatClarinet.EFlatClarinet'>
Return class.
When default_instrument_name matches no instrument class:
abjad> instrumenttools.default_instrument_name_to_instrument_class('foo') is None
True
Return none.