CD of 60s and 70s classic rock? They didn't have electronic tuners back then, then tuned to the studio piano or whatever. It's a nightmare!
i use transcribe too.
regarding the tunings:
it´s not that they didn´t have tuners, there are a lot of different reasons:
ever tried to play to an Van Halen record? To get all this major triads he loved to play sound right, he tuned the guitar differently for each song, you find a lot about that in the web, ie: http://forum.metropoulos.net/viewtopic.php?t=45970
In the analog days it was very easy (varipitch on the 24 track machine) to alter the pitch of the recordings. Slightly faster, slower, and therefore higher or slower playback will change the feel of a song in a HUGE way, done by a lot of artists.
The Beatles already edited together recorded versions of songs in different keys, which was only possible with varipitch, check out Strwwberrie Fields,
and the result is not only somewhere between B andf Bb, will alter tempo between the edited slices, and you still need to retune your guitar in the middle of the song if you want to play along.
When the CD format arrived and old tapes got digitalized, very often nobody cared to calibrate the speed of the tape machine. Donald Fagan (Steely Dan) complained a lot about his songs playing at the wrong speed after the transfer and there are still many CDs and Mp3s around.
Probably many artists never noticed that.