Manually connecting groups of beamed notes with a single beam
Groups of non-periodic beat structure beamed notes can be connected manually with a settable number of beams using the stemRightBeamCount and stemLeftBeamCount properties.
\version "2.24.0"
%% http://lsr.di.unimi.it/LSR/Item?id=927
% see also http://lsr.di.unimi.it/LSR/Item?id=2
%=> http://lilypond.1069038.n5.nabble.com/Beam-subdivided-at-non-periodic-intervals-td164174.html
\relative c''''{
\time 4/4
\key g \minor
\ottava #1
ees16[
\set stemRightBeamCount = #1
d
\set stemLeftBeamCount = #1
f ees
\set stemRightBeamCount = #1
d
\set stemLeftBeamCount = #1
c b d
\set stemRightBeamCount = #1
c
\set stemLeftBeamCount = #1
bes a g
\set stemRightBeamCount = #1
fis]
\bar "!"
}