Lilypond currently supports simple "irrational meters" like 4/10, 7/6, etc.
which are used by contemporary composers such as Ferneyhough, Adès, etc.

However, \compoundMeter cannot handle many of these complex notations.  It
sometimes fails when an irrational component such as 1/10 is included in the
compound meter, and fails when a _fractional_ value such as 2/3 is included in
the compound meter -- as in Boulez' "Le marteau sans maître" where there are
time signatures such as (4 + 2/3)/8 .

I've attached 3 minimal examples, 2 which fail with the compound meter but
compile with the equivalent non-compound irrational meter; and one which
includes a compound irrational meter that works.