Agreed completely about Jon Lord. Even as a guitarist, I think of Jon Lord's organ playing when I think of the Deep Purple sound. Definitely one of the 20th Century's finest musicians.
Admittedly, I've never gotten too much into Deep Purple. I know and love all of their well known albums (Perfect Strangers, Burn, Machine Head, etc) but by no means have I looked into the entire discography. Perhaps I should do that, but I've never heard much praise for that stuff, and despite being a massive Steve Morse fan, (I'd probably even take him over Blackmore) Deep Purple without Blackmore seems odd, and frankly not right, and Morse has such a different style of playing, so I've avoided the albums with Morse. For Blackmore stuff, I go to Rainbow, their style suits me more.
To me, Deep Purple is like rock's version of a jazz group. The albums are a solid representation of the band and their tunes, but to really experience the songs the way they should be heard, you need to hear them live. Which is why I think of Deep Purple as one of those few bands where their best album is a live disc, and that is one that I'll write about here.
Made In Japan - A legendary live album. Deep Purple's Live After Death. Once you hear the extended jams on this disc, you won't want to go back to their studio counterparts. This is how these songs were meant to be heard, extended improvised solos that still fit within the context of the song. The energy on this album is also fantastic, you can hear it in everybody, this truly was a special concert. I really have nothing else to say about it, just something that you should listen to right away if you haven't already. One of the best live albums of all time.
Concerto For Group And Orchestra - Now this is something else. A concerto by Jon Lord that serves as the very first combination of rock band and orchestra. I love this album, my 2nd favorite after Made In Japan. The whole rock band with orchestra thing has been done gazillions of times before, but this still remains to be the best. Here, the orchestra gets its own unique sections and parts, and it's music written with orchestra and band combined, unlike most of these things where the band arranges earlier songs for and orchestra accompaniment. The orchestra on this album is huge, and the piece is epic. I love it, classical music at its best. This is something totally different, but I think it is a good way for a rock fan to be introduced to the classical world. Amazing piece.