I just took a video with my phone, and the audio is so garbled that you can't make much sense out of it.
Since it sounds like a metal on metal rub that increases in intensity with the engine RPM and doesn't seem to depend on the transmission, I did a preemptive oil change today (went from Valvoline full synthetic to Castrol full synthetic). I didn't think this did anything, but when I just went back out to replicate the noise, it has died down in intensity quite a bit.
If this noise was coming from my car, I would be lubing the bearings on any exposed rotating items like the alternator, AC compressor/clutch, tensioner pulley, etc.
I just don't know where this leaves me with a motor that doesn't have those items.
I did also remove the cam chain tensioner (entirely) and checked to ensure that it moved freely when the spring presses against it, then reset it and reinstalled it. This did not make any immediate improvement to the noise.