I've been going through the Silverline Abravanel Mahler/Brahms/Sibelius/etc releases...bargains at $5 or so a pop. That said, the received wisdom seems to be that they're sourced from quad tapes, but I'm not so sure? Some probably are, but many of these recordings were made in the 1960s, before the quad era (E.G. the Mahler 2 is from 1967, while the Rachmaninoff 3rd Symphony dates from 1961, etc). In the documentary about making these releases (Restoring a Legacy or somesuch) the mixing to 5.1 is kind of glossed over, beyond telling us about the awesome stereo A/D converter they used.
So I'm kind of wondering which ones are actually sourced from multichannel, and which ones are upmixes? I know Silverline has had at best a shaky reputation for bad upmixes of popular material, but the sound on their classical releases is generally considered pretty good. Given that classical recordings are rarely that discrete and use surrounds mostly for ambience (with a few exceptions like the Berlioz Requiem - which I don't have but which should be a good test of whether they used the quad tapes), I'm just kind of curious as to whether very many actually originate from quad sources.
So I'm kind of wondering which ones are actually sourced from multichannel, and which ones are upmixes? I know Silverline has had at best a shaky reputation for bad upmixes of popular material, but the sound on their classical releases is generally considered pretty good. Given that classical recordings are rarely that discrete and use surrounds mostly for ambience (with a few exceptions like the Berlioz Requiem - which I don't have but which should be a good test of whether they used the quad tapes), I'm just kind of curious as to whether very many actually originate from quad sources.