3 Chord tremolos look like beams, but are a kind of repeat symbol.
4 To avoid confusion, chord tremolo beams do not reach the stems, but
5 leave a gap. Chord tremolo beams on half notes are not ambiguous,
6 as half notes cannot appear in a regular beam, and should reach the
12 \context Voice \notes\relative c {
13 \repeat "tremolo" 8 { c16 d16 }
14 \repeat "tremolo" 4 { c16 d16 }