That kind of new (around 100 years old) rhythmic values are really useful, and we are still waiting for Notation Softwares to be able to really play those rhythms! And they are not so weird, by the way. For example, the 1/12 note is a plain eight-note at the “speedness” of a eight-note-triplet: you just don’t need to group those notes by three. So for example imagine you are in 4/4 and suddenly you have a 7/12 bar: at that bar you just count “at the speed of eight-note-triple related to the 4/4t” but just until 7… and that bar is over.