Djaef: FM radio is an easy way of describing the quality of the original live on-air radio broadcast.
Let me give you an example. In the early 1970's stereo radio was very rare and very expensive. The Golders Green gig was originally broadcast as part of the BBC Radio One "In Concert" series - but it was broadcast on medium wave for a bigger audience. (Actually it was broadcast on both MW & as an FM experiment - but the latter audience was very small).
Medium wave was a mono lo-fi tecchnology, so although some MW recordings may exist - they are not worth the quality.
By the mid 1980's Radio One broadcast on both FM and MW (the audience was about 50/50) so to show that you had the top notch version - it would be labelled FM version.
These Radio broadcasts could be BBC session re-runs, or interviews, but usually the FM prefix was applied to live concerts. Here are some world wide examples:
Queen: Unreleased Live Mannheim Maimarktgelande, 21st June 1986
Live West German FM radio broadcast 21st June 1986
Queen: Unreleased Live Independent Radio Broadcast Real Magic 12th July 1986
Record July 12th 1986.
Broadcast UK FM Independent radio and television stereo simulcast, October 25th 1986.
Of course, today 2004, it seems unthinkable of the radio as being such a lo-fi medium, as all main radio stations now broadcast in FM, or even digitally - but the easy way to think about this is to use TV as a comparison.
TV began as a black and white medium, but is now fully colourised. Obviously the transition between the one and the other means that in some cases only one or the other version exists - but some "Dr Who" episodes for example exist in both (B&W & Colour), therefore the BBC would now only be interested in the latter version.
So, as a Queen fan, you should only be interested in seeking out the FM versions also!
"Listen to them. Children of the night. What music they make."