Hello Bob,

BP> Is there a way to bypass the hdmi in the monitor to check for output
BP> directly at the Pi's audio jack?

Yes, type at the command prompt one of the following.

audio to HDMI:
amixer cset numid=3 2

audio to analogue:
amixer cset numid=3 1

Automatic (=default):
amixer cset numid=3 0

When HDMI is connected while booting, audio and video goes there,
otherwise it is available at the analogue socket.
That's why you always have to connect and swith on you monitor first
before powering up a Pi, so the HDMI is selected automatically,
otherwise you could have no signal at your screen.
You can also set the config.txt file at the first FAT32 partition.

BP> I've not yet tried rebooting, but will do that as soon as a running
BP> job completes.

BP> Thanks for reading, and any ideas!

I have bad experiences with the analogue audio.
Via HDMI is much better quality, if the (tv-)monitor supports it.
Note: you know the analogue 3,5 mm jack connector has 4 contacts
      for both the stereo sound and composite video.
From the Pi 1B+ on and also the 2B, 3B and 3B+ the pinlayout is:
1 Tip   = Left audio.
2 Ring  = Right audio.
3 Ring  = GND.
4 Ring  = Composite video.
So look for the right cable that supports this in the right order.
CamCorder cables have switched the video and right signals.
MP3 player cable has the GND and Video signals changed,
so do NOT use these at a Pi,
or you can damage some hardware at the modern Pi ;-(.

The old Pi 1B with only 512 MB memory, 2 USB sockets have a 3 pole stereo
audio Jack besides a yellow Chinch/Tulp composite video socket.
So good luck with the audio.
I hardly use it as I am very hard of hearing,
but you may get better results.

Greetings from Henri.

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