Short take: Buy it for the music if you like it, but NOT for the surround.
I think I can shed a little more light on this title than has appeared here previously.
This recording documents a concert from the Royal Albert Hall from 9/24/69 featuring the classic "Mark II" lineup of Deep Purple. More can be found on the various line-ups here:
https://en.wikipedia.org/wiki/List_of_Deep_Purple_band_members
The Music:
For rock fans, there are three "band only" songs on this disc: Hush, Wring That Neck, & Child In Time. This is the classic Deep Purple playing at or near the height of their career, so this document of the concert is worthy for any Purple fan. If you don't like classical, you can just play these three tracks, presented here (on the DVD-A & SACD) in high resolution.
For classical fans the disc begins with three movements of a symphony by the orchestra alone, with no Deep Purple. I am not a classical fan, so there is no point in me commenting on this performance. Others may wish to chime in.
The final section of the disc is the performance which includes both orchestra and Purple. This was written by Jon Lord and to my knowledge not performed by Purple in any other context than with an orchestra. I mention this because around this time Pink Floyd was also preparing Atom Heart Mother, which they often performed without the orchestra, and I think this speaks to the nature of the music. I am not sure the Deep Purple orchestral piece would have stood up to a band-only performance, although I am no Deep Purple expert, so forgive me if they tried it and I am unaware of it.
Do I like the combined piece? I find it to be a curiosity, and not unpleasant to listen to. But I doubt I would give it many repeated listenings, because as I noted earlier I am not a classical fan. Those who love this band AND classical might find much to like here.
As previously mentioned earlier in the thread, the rears are hall ambience ONLY. There is no discrete content whatsoever in the rears. I have never understood the appeal of this sort of mix, but others around here obviously enjoy it, especially if in a classical context. Deep Purple obviously have mixed other things in surround, so the concept is not entirely foreign to them, although as of the fall of 1969 very few bands or engineers were thinking in those terms.
I am really not knocking the music here, but with surround in mind I cannot go more than a 5. In fact, if surround were the only criteria I call this a solid 1, but with the high resolution music in mind I cannot call this a waste of plastic, as would be suggested by a 1.
With the high prices this seems to fetch these days I would say this is for the hardcore Purple fan only.