I don't know if it's been discussed before but I'd like to know more about the more technical side of their records... does anybody know anything about that or can point me in the right direction?

All I know is what I've read on Felder's book, about them doing take after take after take of the guitar solos and the vocal parts until they were virtually flawless, etc., but I'm sure there's a lot more to be discovered, such as:

* How did they synchronise? Did they use a live backing track as guide (like Pink Floyd, Led Zeppelin, etc.) or did they use a click track?

* Did they always record backing vocals in a way that could be reproduced on stage and, if so, does it mean they stayed away from the 'self-backing-vocalist' trick?

* Anything related to session musicians (orchestras and the such) and the way they recorded with them, who took care of that, etc.

I appreciate anyone who can give me a hand with *any* of that