I’m loving these Songsmiths recordings. Songs played in their simplest form captured by one mic. Simple, beautiful.
Recording acoustic guitar and a vocal with one mic eliminates the phase issues that can crop up when using separate mics on voice and instrument. In that 2-mic scenario, each mic picks up a bit of what the other is meant to capture, so if the mics aren’t placed properly, the waves can actually cancel each other at certain frequencies. Also, the sound of the vocal in the guitar mic will be a “distant” sound and vice-versa. Not necessarily desirable.
While I know how to minimize these issues, I still think the clarity of the one mic recordings is superior. Plus, the best way to do a 2 mic recording wouldn’t look good on camera. There would be a mic in front of the artist’s face, and perhaps a divider between the guitar and the artists mouth if necessary to reduce bleed. I know I wouldn’t want all that going on when I’m trying to perform at my best.
The challenge of recording with one mic is that you have to get the voice/guitar balance right when you record because you won’t have much control over that when “mixing”. So, put on a pair of headphones and move the mic around until the voice can be heard clearly over the guitar. I use a condenser in omni with the front of the mic pointing at the singer’s mouth. Even in omni, the mic picks up more high-end info from the front which helps the vocal stand out. You will also want to make sure that you’re getting a good guitar tone which you might not get if the mic is placed in front of the singer’s mouth. In that position, the mic may be over the neck not the body of the guitar, and the sound can be thin. It sounds like I’ve just contradicted myself, but it is possible to point the front of the mic at the singers mouth from a position closer to the body of the guitar. 
Once recorded, play with your compression settings to get the balance and vocal sound. You might be surprised by how much control you have over the balance of the recording despite the fact that it’s only one track. Add EQ, reverb, etc. to taste.
Note that I wouldn’t recommend recording final guitar and vocals this way if you’re going to be adding other instruments. In that case, you will probably want to be able to edit, balance, add effects, etc. to each instrument individually. The one mic technique is, however, a great way to lay down a guide track in one shot. Once recorded (with a metronome), you can overdub drums and the rest of the instruments. The guitar/vocal is the core of the song and is enough to go on to begin production.
Great job and good luck Matt!

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