Walter Meyer wrote:

>I think it was possible to get an hour's worth of music on an lp recording.

Actually it was possible to get much more. There was a set of LPs of the
Ring...11 discs!

This was accomplished by reducing the dynamic level.  For that recording,
the Furtwangler La Scala performances it was not terribly problematic since
the source recording used was not very good.  With a reduced dynamic level
one reduce the space between the groove.  The deeper (to allow for a wide
dynamic range) the greater the need for space.

One of my favorite stories in relationship to this consideration comes
from the first recording of the Vaughan Williams Sixth Symphony.  The last
movement is at a very low dynamic level.  In an effort to improve upon the
audio quality and reduce the noise, the engineer raised the level on the
sides for that last movement so they were as loud as some of the louder
parts of the other movements.  As I recall the composer was not pleased
and insisted that it be repressed!

Karl