We should take attention to different factors :
First I will take the Beatles example : they signed a contract with emi and with the exception of Let It Be, 99% of the recording were made inside EMI studio. That mean in this case that the record company physically owned the master tapes. AND EVEN IN THAT CASE THERE ARE LOST BEATLES RECORDING.
Second I will take the ROLLING STONES example : an executive producer is commissioned by record company and the recording is made outside of the record company. That mean in this case that the record company physically DOES NOT own all the master tapes. In the case of the Rolling Stones for the sixties their are in the hand of ABKO (Allan B. Klein Organisation, short time manager manager of the Rolling Stones).
Third "outside recordings".
TV and radio show have been airing multiple concert and again the important point is who is the LEGAL producer because it is him who is doing the live airing and if so recording.
The Pink Top festival is known to be partly lost (presumably erased)...
From what I know a big DS fan got hold of a copy off of the master of Sydney video broadcast but what happened to the audio tapes?
What happened to the Wembley audio and video 1985 ?
What happened to the Werchter 1981 audio and video tapes?
The 1978 BBC recording seems to be safe?
What happened to the NHB audio and video tapes?
What happened to the Mandella audio and video tapes?
Etc.
The only exception are for recordings made BEFORE the band signed with Polygram but all subsequent recording, they are all owned by private company but can't be published until they get a deal with Polygram as it happened for the BBC tapes and even for three songs from the Pathway Demo EP (whereas Sultan Of Swing demo has been first issued on Oval record).
And last but not least, holding of the master tape in one thing,but the legal question is another. If only one right holder is in position to say "NO" the thing can't be published.