[Scott Dorsey]

Adrian Tuddenham wrote:

I think the wax stays smooth but becomes too hard for the cutting tool
to work smoothly. The tool chatters as it tries to cut the hard wax.
If it has been heated or cooled unevenly, the effect will vary around
the axis of rotation.

Yes. I blame a poor tool as much as I blame hard wax for this, though.
You can even make it happen with a lacquer if you use a worn cutter,
even hot.

The biggest component on the disc is probably longitudinal ('Z'-axis)
modulation which would give a frequency-modulated effect, but this won't
be visible or strongly audible. Any lateral component of the chatter
will be much more audible. and may be visible under the right
conditions.

Yes, the longitudinal vibration is manifested as a kind of flutter that
produces sidebands around pure tones. But there will also be lateral
vibration too, and it should mostly be at the top of the groove where
the wax is more free to move up and down.

I have never actually cut wax... it would be really fun to try and see
how different it is than a modern lacquer.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."