Yes, an interact callback.
What you do is, that you go into the properties of the note.
There should be a box you can write in, called something with "interact" or "interaction" (I don't fully remember)
In this box you write the function you want to be called.
Let's say it is "InteractNoteVoice"
Then in your script you write the same function, so the game knows that if you interact with the note, THAT is the function it's gonna call. Like this:
void InteractNoteVoice(string &in asEntity) <-- If you don't understand what these are, then try check this link:
http://www.frictionalgames.com/forum/thread-18368.html
So the full function should look like this:
void IntertactNoteVoice(string &in asEntity)
{
AddEffectVoice("voice01", "", "Voice", "invoice", false, "intro_note", 0, 0);
}
Remember to put the function in the properties of the note too, in the level editor.
Trying is the first step to success.