New in version 2.6.
True when expr is a sequence of Abjad voices:
abjad> voice = Voice("c'4 d'4 e'4 f'4")
abjad> voicetools.all_are_voices([voice])
True
True when expr is an empty sequence:
abjad> voicetools.all_are_voices([])
True
Otherwise false:
abjad> voicetools.all_are_voices('foo')
False
Return boolean.
Function wraps componenttools.all_are_components().