This topic arose from another different issue and I thought deserved it's own thread so I could pass on what I have learned in making a video using the video function of the Nikon P7100. In particular, I learned that it was possible to use the 'hotter' line out from an acoustic guitar amp, to record vocals and acoustic guitar in stereo directly into the more 'sensitive' mic input of the Nikon.
This is the test video of me doing an acoustic cover of Tomorrow Never Knows. There is also substantial text in the background under the video in youtube which details how I made the video and solved certain problems, although not all.
I hope it is some use to both Nikon users and musicians. It certainly has been and still is a learning process for me.
Regards from Mike