Just stating the obvious, but... WCS, if the '1st-gen copy' isn't edited in a major way, you can always resort to the two-pass/assemble method:

VIDEO FROM THE MASTER TAPE + Hi-Fi AUDIO FROM THE COPY

Of course. Thing is, who knows how much of the material is present as a copy. So far, it's very little and I doubt it's a significant amount.

I'll try to get some more info from the taper and check out a few more VCRs. Will post when there are news.

Separate camera and VCR or camcorder?
Any idea what kind of camera it was?
Professional or Consumer?

Consumer camcorder build-in mics were and still are generally pretty "dog meat." They typically had a high noise floor and limited frequency response. External mics at the camera from that era were better, but still may have limited frequency response if anything but professional class gear.

I can't tell from the limited AVI, but other portions of the video may give more clues. Information such as ambient and audience noise/applause between numbers, camera views, announcements from the stage mic, and instrument balance can give clues as to mic placement.

Have you tried to pull the linear audio off the First Gen to see what it looks/sounds like compared to the master?

Today I ran a few audio tests on an AG-1980. They included recording a 1 kHz tone, some white noise, and a sine wave sweep from 1K to 18 kHz. These were recorded to both the HiFi and Linear tracks on a freas (if old) Memorex HS VHS tape. I than played the tape in the same machine and captured playback with a M-Audio Delta-66 sound card and Audition 3.0. The attached PDF file shows several wave forms and spectral displays from the capture. Why only 18 kHz - because only dogs and 16 year olds can hear above that.:))

Conclusions

- The AG-1980 provided a reasonably flat linear track in self-record mode, down about 3 dB at 10 kHz and after that it falls rapidly, down 16 dB by 12.7 kHz. However the HiFi track was flat out beyond 18 kHz.

- The AG-1980 linear track output appears to actually have a bit of a "notch" filter, probably to suppress audio around the horizontal frequency. This is evident in the spectral display and the frequency analysis display, where the noise floor rises to a shelf level above 15.7 kHz. The HiFi track has a consistent noise level (no notches)

- Harmonics (especially 2nd and 3rd) are evident in both the linear track, but to a much lesser extent in the HiFi track. (Probably around 1% distortion.)

- The Spectral frequency display shows that the linear track contains some sweep audio out to 18KHz, and its harmonics to the limit of the sampling rate (48 kHz). I do not know whether these are bleed or real, but the overall levels are low.

- The linear track white noise recording level show clears shelving above the "notch" frequency.

Interestingly, the JVC HR-S3500U I have does not have the "notch" filter on its linear track's output frequency response. Further, the Sweep output from the AG-1980 tape shows marked indication that its audio head azimuth did not matching that of the AG-1980. The effect on the captured waveforms is dramatic. (The alignment issue was verified by a self-record test with the sweep.) The JVC linear track self-record test also did exhibited aliasing, horizontal frequency bleed, and other issues that made the output look like garbage on a technical display, although much of that is probably not audible to most listeners.

Bottom line on this is one can not trust linear track head azimuth alignment when moving from one machine to another, especially if the machines have not been aligned recently to the same standard.

This brings to mind the possibility that the HiFi track on the First Gen might sound better because is is not tainted by potential linear head azimuth alignment variation compared to the master tape's recorder.

On the subject of linear track azimuth alignment impact, there is not much out there on VHS, but there is a lot on audio cassettes.

The linear track on VHS (for mono) is 1 mm wide and the tape speed is 1 5/16 IPS. In contrast the track width on a audio cassette is 0.6mm and the tape speed is 1 7/8 ips. (The faster tape speed will give the audio cassette a wider frequency response for the same tape head gap. The narrower track will make head azimuth less critical for the same gap.) So while the figures for a VHS linear track will not match those of an audio cassette, the general principles do apply.

The attached graphics shows the effect of head azimuth misalignment on frequency response. This is for a high end Nakamichi deck with a rated frequency response more than double that of VHS linear track, but one can see the effect of even a slight misalignment measured in (minutes of angle).

Because alignment errors can be found in both the recorder and the playback machines, for best results the playback machine linear audio head should be aligned to the tape being played. (Alignment to a standard test tape will improve interchangeability with other properly aligned machines, but may not give optimum playback of a given tape.)

(FWIW: The HiFi tracks do not face this issue.)