StemTremolo grob it is possible to control the appearance of tremolo slashes.
Property slope sets the slope for tremolo slashes.
Property shape determines whether tremolo slashes look like rectangles (value rectangle) or like very small beams (value beam-like).
Property style sets both the slope and the shape depending on whether the note has flags, beams, or only a plain stem. This is in contrast to the previous two properties, which change the slope and shape unconditionally. There are two styles defined.
default: slashes for down-stem flags are longer and more sloped than slashes for up-stem flags; slashes on beamed notes have a rectangular shape and are parallel to the beam.constant: all slashes are beam-like and have the same slope except for down-stem flags.