I like the idea overall. Looks like something that would be fun to combine with music programming languages (SuperCollider/Of etc).
Not so sure how human-friendly the fractional beats are? Is that something that people more into music than I am are comfortable with? I would have expected something like MIDIs "24 ticks per quarter note" instead. And a format like bar.beat.tick. Maybe just because that is what I am used to.
It should be fine, but fractions (or both fractions and decimals) would be preferable in order to express triplets (3 over 2, effectively a duration of 0.3333...)
The library has MIT license, I would be more than happy to see people use it in different synths.
I'm planning to add support for math formulas in beat numbers, something like: "15+/3+/4" = 15.58333