I'm currently using version 2.12.3. I've noticed that sometimes Lilypond uses sloped beams, and sometimes uses level beams, in places that appear to be almost identical. Specifically, see the snippet in the Learning Manual, Section 1.1 Background ="" What symbols to engrave,
%ly snippet: \sourcefileline 564 \include "engraver-example.ily"
The upper voice has 4 beamed 16th notes, and the beam is sloped. The lower voice has a similar construction, and the beam is level. Any reason for this? I prefer the sloped beams.