Comment #29 on issue 2246 by [email protected]: beaming in 3/4 - a setting to not beam 3 eights against the beat.
http://code.google.com/p/lilypond/issues/detail?id=2246
[Editing my ambiguous comment 28] The proposed patch for issue 2566 gives the option beamMidMeasure to control specifically the pattern that gives the impression of 6/8 time: starting a beam of eighths mid-measure.
That patch sets the default at beamMidMeasure = ##t, to engrave r4. c[ c c] as in the Classical period. Then we can choose the modern recommendations with beamMidMeasure=##f, or strict beaming-to-the-beat with \unset beamExceptions.
