Customizing tremolo

[Thomas Morley]

Hi,

this arose in the german forum about typesetting tremolos for
https://imslp.org/wiki/String_Quartet_(Carre%C3%B1o%2C_Teresa).
https://lilypondforum.de/index.php/topic,1091.msg5888.html
An excerpt of Vl 2 is attached.
In measure 8 there are tremolos with one connecting beam and one
floating beam lasting a quarter note.

How to do so?

Obviously we establish a certain default, but I'm not able to override
the default with Beam.gap-count in every case.
Although even non-tremolo Beams react:

\relative c'' {
  %\override Beam.gap = 0
  \override Beam.gap-count = #1

  \repeat tremolo 16 { a64 f }
  \repeat tremolo 8 { a64 f }
  \repeat tremolo 4 { a64 f }
  r8
  \repeat tremolo 8 { a32 f }
  \repeat tremolo 4 { a32 f }
  \repeat tremolo 2 { a32 f }
  r8
  \repeat tremolo 4 { a16 f }
  \repeat tremolo 2 { a16 f }
  \repeat tremolo 1 { a16 f }
  r8
  \repeat unfold 16 b16
}

Am I missing something?

Thanks,
  Harm

Carreno-Vl-II-excerpt.png
Description: PNG image