5 Stem tremolos or rolls are tremolo signs that look like beam segments
6 crossing stems. If the stem is in a beam, the tremolo must be parallel
7 to the beam. If the stem is invisible (e.g. on a whole note), the
8 tremolo must be centered on the note.
14 \context Voice\notes \relative c''{
15 \override TextScript #'direction = #1
16 \override TextScript #'padding = #5
17 a1:4^":4" a:8^":8" c:16^":16" a:32^":32" a^"x" a:^":"
18 a4:4 c:8 a:16 c:32 a a: a2:
27 c,16:32 c: c c a16:32 a: a a