[Dobbin]

You don't get much more durable (in comparison to all the other formats)
than analogue tape, safeties were always one to one copies. The
recommendation for archiving audio is still analogue tape, whatever the
source. It should to be stored tails-out in a humidity and temperature
controlled environment and carefully wound every few years.
There have been problems with hydroscopic tape, binder breakdown and
shedding, particularly Ampex from the 70's and 80's, and sticky edits but
all these can all be repaired with careful manipulation. Analogue masters
are nowadays transferred to digits for working copies but the originals are
retuned to their archives.
You could run a 2" tape quite a lot on a well maintained machine, sometimes
when the degradation became audible, starting with slight top loss at the
edges first (put the bass on track one!) it gained it's own new quality - I
doubt Bohemian Rhapsody would have sounded so good and graunchy on radar.
Loose a bit of top, get a bit of hiss and maybe slight level dropouts on
analogue or you could get absolute silence (I.e. nothing at all!) back from
your digits.
One day the audio world will agree on a digital archiving standard; on
standardised retrieval machinery and then maybe process can begin to go
forward

wrote in message
oups.com...
I assume that the master tracks of the Beatles, etc. have all been
transferred to more durable optical digital - i.e. CD or DVD. But back
in the days when tape was all there was, what measures were taken to
protect/backup masters?

Seems precarious that hundreds of expensive hours of work for an album
were riding on a few mils of plastic tape coated with a few microns of
oxide.

And what about multiple takes - how many times could a tape be run
through the path before it shed enough to be audible?