from there the music shield will store the audio onto an SD card. I reviewed the liberay code that comes with the shield and it does seem like this is possible.
my question is will it accept the UHF speaker line into the mic input of the ardunio?
resolved? - maybe, its called audio feed back loop. although you cant just plug any leads in. line to line audio (not stereo to line) is what you want and i suspect that VHF is line out as its just one speaker. i know the shield is line in. so this theory is probably correct!
what i'd like to do is splice the cables with 2.5mm stereo joiners (male/female)
3.5mm is normal for stereo. Are you sure its stereo at all?
I would add a series 1k resistor in the audio path to protect the input circuit - a speaker
output can drive high currents and potentially do damage, 1k will limit the current and
protect.
I theory this ought to work, although microphone inputs are very sensitive and the
level may be too high (a resistive divider can then be used).