stopTrillSpan

[James E. Bailey]

I'm sure there is, and I just can't think my way around it, but I'm  
having a problem with a trillspan that starts in a one-voice context  
and ends in a two-voice context.
Like this:
\relative c'{
        \pitchedTrill <c g'>1\startTrillSpan a   |
      <<\relative g'{g1\stopTrillSpan}\\\relative c'{ c2 b}>>
}

Right now, my workaround is to use:
\relative c'{
        \pitchedTrill <c g'>1*3/4\startTrillSpan a  s4\stopTrillSpan |
      <<\relative g'{g1}\\\relative c'{ c2 b}>>
}

But I'm wondering if there's a way to do without the spacer notes.