I have beenproducing high quality 2 mic audio recordings for many years, including recordings of mainly classical and choral concerts. A number of years ago I was asked to also make a video of some of these concerts. Most camcorders do not have audio that is good for music concerts because even if they record using 48kHz/16 bit sampling, they have AGC circuits (automaic gain control) which basically eliminate almost all of the dynamics, which are especially important for music. While I have tried using the audio I record on a separate recorder as the audio for the video, getting everything in sync was frequently difficult.
For the last 2 or so years I have been using a Canon Vixia camcorder that has proven to be the solution for gettingCD quality audio with the video without the hassles and problems of attempting to sync aseparate audio source file. TheCanon Vixia line of camcorders (I think all of them)enable you to set the audio level manually (thereby turning off the AGC circuits) and alsoallow you to turn an input attenuator on, permitting you to input a line level signat to the mic inputs of the camcorder. This means that you can take the line level output of an external recorder (or mixing board if you need to go that route) and record it with the video, eliminating any potential sync problems.
The equipment I have been using is a Tascam HDP2 recorder (that includes mic preamps), a matched pair of Earthworks QTC40 mics, and I connect the line out from the Tascam to the mic input of the Canon Vixia camcorder, making sure that the audio recording level on the Vixia is set to avoid overloading (i.e., it matches or reads a bit lower than the meters on the Tascam).
If you'd like to see some of the results, look at my videos on YouTube, posted under the name bsellman2. Concert videos of Dolce Suono were recorded using the equipment listed above. There are also a few informal videos posted that I made using just the camcorder's mics; however, I'm not sure which ones had the AGC turned off. Here's a link to one of the Dolce Suono videos:
For comparison you can hear samples of the CDs I released, many recorded with the same audio equipment, by visiting my website www.dtrmusic.com
The article in a recent Videomaker talked about using small portable recorders, but syncing up during the editing process. The same process I mention above could work with a Canon Vixia and one of the very small portable recorders for work where you need to be able to move around. And just turning off the AGC can greatly improve the audio even when you use the camcorder's mics. With recording at CD quality you can do a lot of audio level adjustments in your editor without getting excessive added noise (if you have to raise the levels a lot at some points).