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WTF is going on here? Triggering External Audio via Grounding on Arduino

I'm using Fizikus' design to add audio cues to a project.  The schematic, from Ar-Du, looks like this:

We're both using Arduino as the brains to the project.  I've run into a little snag though.  The problem is that apparently you can't actually trigger the audio cue this way because the trigger pin has to go low to trigger it (in this case, that doesn't translate into digitalWrite (triggerPin, LOW)-it means instead that you have to connect that pin to ground.)  

My solution was to set the output pin up on the base of a 2n3904 w/collector to ground and emmiter to the unit.  Then to test it, I set up a standart pushbutton switch with a resistor to ground on another pin. 

The result?  The pushbutton doesn't work, but if you touch the wire running from the touch switch to the input pin, IT DOES!  It's like an unintentional proximity switch.

So to test it further, I uploaded a second sketch that just triggered the output pin high for ten μSec then low for 10 seconds.  Nothing.  Uploaded the original sketch.  Nothing again.  

Short of putting a solid-state relay on a transistor, anyone got any ideas here?  I'd rather not have to use that solution.  (I tried a JFET already to no avail.)

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You need to connect your pin with a 10k resistor to VCC to keep it HIGH until you write it LOW. A so called pull-up-resistor

Thanks! Wasn't sure about that. I'll give it a try when my head stops throbbing.

Thanks again Gabriel!  The documentation on this chip is actually fairly good, but as they say, "There's a special place in hell for the writers of semiconductor manuals."