4 Tremolo repeats can be constructed for short tremolos (total duration smaller than 1/4) too. Only some of the beams are connected to the stems.
7 \layout { ragged-right = ##t }
10 \context Staff \relative c' {
11 \repeat "tremolo" 2 { c32 e32 }
13 \repeat "tremolo" 2 { c32 e32 }