True when 1/2 < multiplier < 2.
abjad> for n in range(17):
... rational = Fraction(n, 8)
... multiplier = tuplettools.is_proper_tuplet_multiplier(rational)
... print '%s %s' % (rational, multiplier)
...
0 False
1/8 False
1/4 False
3/8 False
1/2 False
5/8 True
3/4 True
7/8 True
1 True
9/8 True
5/4 True
11/8 True
3/2 True
13/8 True
7/4 True
15/8 True
2 False
This function models the idea that 4:3, 4:5, 4:6, 4:7 are valid tuplet multipliers while 4:2 and 4:8 aren’t.
Changed in version 2.0: renamed durationtools.is_tuplet_multiplier() to tuplettools.is_proper_tuplet_multiplier().