>As to 78 rpm: regular spokes I have only seen on lacquer recordings, whereas
>a similar phenomenon is not unknown even on acoustic recordings. The surface
>then looks like moiré silk, and it is actually a constant number of vertical
>vibrations per second not tied precisely to the rpm, so the spokes are
>"crooked". This was usually a cause for discarding a take, so they are
>uncommon.

I suppose another possibility might be a burr in a gear or some other 
deficiency in the recording mechanism that would result in a frequency that 
becomes visible in the recording.

Occasionally the music itself might have a rhythm or repeated phrase that 
results in a radial pattern of some sort (especially in audio test 
records), but this looks different from the spoking mentioned above.

Kurt & Diane Nauck

c/o Nauck's Vintage Records
22004 Sherrod Ln.
Spring, TX  77389

Website: www.78rpm.com
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Phone: (281) 288-7826
Fax: (425) 930-6862