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Subdividing beams

The beams of consecutive 16th (or shorter) notes are, by default, not subdivided. That is, the beams of more than two stems stretch over the entire group of notes without a break. This behavior can be modified to subdivide the beams into sub-groups by setting the property subdivideBeams to #t. When set, beams are subdivided at (rhythmic) intervals to match the metric value of the subdivision.

Using the properties beamMinimumSubdivision and beamMaximumSubdivision it is possible to configure the limits of automatic beam subdivision, namely the minimum and maximum rhythmic lengths at which beamlets are removed. The default values are 0 for the former and +inf.0 for the latter, making LilyPond subdivide beams as much as possible.

There are two special cases to consider.

• If the numerator of beamMaximumSubdivision is not a power of 2, the rhythmic lengths considered for subdivision are beamMaximumSubdivision divided by powers of 2 that stay greater than or equal to beamMinimumSubdivision.
• If beamMaximumSubdivision is smaller than beamMinimumSubdivision, the depth of beam subdivisions is limited by beamMaximumSubdivision, but not the frequency and rhythmic intervals, therefore possibly deviating from the correct, expected metric value.

If respectIncompleteBeams is set to #t, incomplete subdivisions with more than two stems are treated as an ‘extension’ of the previous subdivision group, i.e., the length of the previous subdivision group gets extended to also cover the incomplete subdivision. If set to #f (which is the default), a new subdivision group gets started instead.

\relative c'' {
  \time 1/4

  <>^"default"
  c32 c c c c c c c

  <>^"with subdivision"
  \set subdivideBeams = ##t
  c32 c c c c c c c

  <>^"min 1/8"
  \once \set beamMinimumSubdivision = #1/8
  c32 c c c c c c c

  <>^"max 1/16"
  \once \set beamMaximumSubdivision = #1/16
  c32 c c c c c c c

  <>^"max 3/8"
  \once \set beamMaximumSubdivision = #3/8
  \repeat unfold 16 c64

  <>^"min 1/32, max 1/64"
  % Set maximum beam subdivision interval to 1/64 to limit
  % subdivision depth, despite not being metrically correct.
  \once \set beamMinimumSubdivision = #1/32
  \once \set beamMaximumSubdivision = #1/64
  \repeat unfold 32 c128
  \break

  <>^"beams with incomplete subdivisions"
  c32 c c c c c c r32
  c32 c c c c r16.

  <>^\markup { "the same with"
               \typewriter { "respectIncomplete=#t" } }
  \set respectIncompleteBeams = ##t
  % The incomplete subgroup extends the completed subgroup.
  c32 c c c c c c r32
  % No visual change since we have only two stems in the
  % incomplete subgroup.
  c32 c c c c r16.
}