also have a resolution of 0.001" or 0.0254mm step.
= more than "20 grooves per milimeter."
the cutting shape can be drawm in software.!!
it would have steady groove separations, not variable volume grooves but...
http://en.wikipedia.org/wiki/Gramophone_record#Structure
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Vinyl_groove_macro.jpg/800px-Vinyl_groove_macro.jpg)
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Vinyl_disc_detail_2.jpg/615px-Vinyl_disc_detail_2.jpg)
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Vinyl_disc_detail_1.jpg/600px-Vinyl_disc_detail_1.jpg)