Actually, the mono track is almost or entirely from a single source–an OTA TV broadcast. I think h_h modified the Fox fanfare at some point, but that’s it. The mono track hasn’t been changed at all in a very long time–I’d be very surprised if the 2.7 track wasn’t bit-identical to the 2.5 track. I tried an ill-advised attempt to merge with non-Dolby 35mm captures at some point, but it thankfully never made it into this project. My only guess is that maybe you’re hearing the lossy core of the lossless track this time, due to a DTS-MA decoder issue in the playback software. DTS-MA lossless mono is a bit of an odd fish–lots of software decoders have issues with it, even though it’s perfectly within the specs. So you might have a decoder that works fine for DTS-MA multichannel and dual-mono, etc, but fails on true mono.