Just to really mess with us all, it looks like the PAL DVD is also mono. Just dual mono, rather than 1.0. But it's encoded as Dolby Surround, because... well, I guess we can't have a release of THE SWORD IN THE STONE without messing up something really dumb, right?
I did my usual test: invert one channel, mix down 2 -> 1, see if there's anything meaningful left. The only residual noise left after this was some whooshy phasey noises presumably from alignment not being 100% perfect before the mixdown. Everything else phase cancelled, indicating that it looks like it's all mono.
Whilst dumb, that's good news: it means we now have at least three sources for the original mono...
1. US CAV LaserDisc (I've assembled the three sides of the less ruined version of the 44.1 kHz PCM audio into a continous, 1-channel, in-sync track)
2. Early PAL DVD (sped up due to PAL, but I've resampled it to 24/1.001 fps; Dolby AC-3, 2.0, 192 kbps)
3. US Blu-ray Disc (haven't yet investigated but wouldn't surprise me if it sounds worse; Dolby AC-3, 2.0, 192 kbps)
And, I'm guessing that probably *also* means that the first US DVD has the mono as well, despite advertising "Dolby Surround".
I hate to tell you, pals, but encoding a 2-channel mono track as "Dolby Surround" does not actually make it a Dolby Surround track. I mean, technically, it does, sort of. But in practice, it's... pointless, apart from that it means you can claim the disc has Dolby Surround, even though you're basically lying.
At first glance, the Blu-ray mono just looks like a hyper-cleaned version of the DVD mono, which seems to in turn basically just be the less-ruined LD mono track but as 2.0 instead of 1.0 (since on the LD it only appears on the left channel, then right channel on side 2, then left again on side 3):
Buuuut to be fair it doesn't look like there was a whole bunch going on above 10 kHz anyway and what was there may just be noise rather than anything meaningful. I haven't done one for the fully assembled audio yet but here's side 1 again (the one on the left is the one I'm actually going to use, since the other channel is garbage):
Notice there's a gap then a chunk of blue there, so I'm guessing that the gap is pretty much where the actual soundtrack (as recorded) ends, then the blue lump is analogue artefacts like magnetic tape hiss.
Hmm.
Also: I didn't mention it before but I wonder what that gap around 900 Hz is? Is that *also* an attempt at noise reduction, of some other sort, possibly some sort of electrical hum or whatever that was picked up by the recording? I wonder.