I have only found only one instance of a song change. In "Mike Fright" where Johnny says on the air to people to take your garbage down to City Hall, just before the opening theme, they substitute Chuck Berry's "Rock and Roll Music," with some generic junk that sounds like an ABBA rip-off.
"'Extremely High Voltage.' Well, I don't need safety gloves, because I'm Homer SimpsZZZxxxxssss" - Frank Grimes

There are a handful of scenes where they were able to replace the music but keep the original dialogue. There are a few other scenes where they had to replace the music AND the dialogue. (Only a very few of those.) And, there are a spot or two thwere they took out the music and didn't replace it. And there are very few spots where they just had to edit a bit but again, those are few.
I think most of this can be blamed on two things:
Music owners flat-out refusing to license their content; and
The original tapes being damaged or unavailable.
But even with these thoughts, I would say that at least 99.5% of the best "moments" of WKRP have survived.

Shout!Factory is supposed to be releasing a complete series DVD box set in Oct 2014. Tim Reid (Venus) says that it will have "most, if not all" of the original music. Rumor has it that they're about 85% of the music licensed so far.
We'll see.
Besides music gone, I'm worried about scenes being cut. Apparently, the budget on the original show was tight, so music was recorded on the same track as dialogue. So if the music can't be cleared, they can't even replace the musicthey just have to cut the scene. This is what happened in a lot of places in the original DVD release.

Shout!Factory is supposed to be releasing a complete series DVD box set in Oct 2014. Tim Reid (Venus) says that it will have "most, if not all" of the original music. Rumor has it that they're about 85% of the music licensed so far.
We'll see.
"As god as my witness, I thought turkeys could fly." Arthur "Big Guy" Carlson

This message has been deleted.

"Dodo I hear dogs barking on that thing?"
"I do."

just stumbled across this today:
http://www.youtube.com/watch?v=Qb-gdaHkbmM
And then compared it to my DVD. I knew the music was editted but I didn't realize how much they cut out on the DVD. The last 45 seconds of the clip are missing on the DVD release.

Thank you very much for the info!

If I recall correctly (it's been well over a decade since I saw that episode with the original music), it's "Dogs" from Animals.
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Oh spiffing. Absolutely spiffing. Well done. Two dead, twenty-five to go.
-Basil Fawlty