Hi, Csounders!

I asked about it already but did not get any answer.
Say, I need to construct "hi-hat" using loscil and
two audio files "opened_hi-hat.aif" and "closed_hi-hat.aif".
How better to provide turnoff of "opened" note if  "closed" note
begins to play? I mean working with MIDI, of course.

Thanks in advance,