global hot-keys during slideshow?

Hi everyone,

Please advise me if you can see a solution for me.

I am recording narration for a slideshow using my JabraBT8040 bluetooth headset. It works fantastic for my needs, except for this problem:

When I have an embedded audio clip playing in the presentation, the headset picks it up, and adds it to the narration recording with a slight time lapse. So, when I play the recorded slideshow, there is an echo in the recording: the slide is playing the embedded audio, and the narration is playing the recorded audio with a bit of delay. This is unacceptable to my usage (I'm teaching a weekly class and posting the video).

I thought I could just mute the headset when the audio in the presentation is playing, but activating the mute switch on the headset does not mute the sound that it sends to system input. This is the case both for my Jabra headset and my Plantronics 903+ bluetooth headphones.

I created custom Services using Automator to mute and unmute the System Input Volume, and assigned hot-keys to it so that I could manually mute/unmute with the keyboard, but apparently Keynote does not allow global hot-keys to be used while it is running in presentation mode. (Is this true?)

Both from the headset device side, and the Mac system side I have run out of ideas. Can you think of any? I'd love to hear what you have to suggest.

Sincerely,
James