Return True when duration ‘duration’ is rational-valued and of a form acceptable for assignment to written duration of a note, rest, chord or skip.
That is, ‘duration’ must be a rational p/q, such that p/q is strictly greater than zero and strictly less than 16, with denominator q a positive-valued power of two, and with numerator p of a form that can be written without recourse to ties.
Otherwise False.