Musical Disk

The musical disk is an obsolete method of information storage which was primarily used to provide the notes of a song in primitive clamourers.
Although it had a profound effect on the entertainment automaton industry, it was soon replaced by punched card and sound-wave carriers, for digital and analogue information respectively.

Utility

In the early times of this kind of technology, it was used for storing digitally encoded information, with some mecanical calculators using it similarly as punch cards.
The usage in that realm was rather limited due to the restricted capacity of such a disk, while it was much more suited for the musical industry where looped tunes could make direct advantage of the disk's geometric features.

Manufacturing

With enough patience and planning, such a disk can be produced with a plain plate of tin and a needle and hammer.
The inner circles are the lower notes whereas the outer ones are higher which, due to the nature of the speed a circle turns, allows the higher notes to be played more frequently then the lower notes.

Access & Availability

While an original plate is a prized collector's item, the plates themselves are extremely simple and cheap to manufacture, making it very simple to have a custom disk made.
It must be noted that the quality of such a plate is considerably inferiour to the modern sound-wave carrier, which is also fairly easy to manufacture.

Discovery

It is said that a horologist of unknown name was observing a potter at his potting wheel when they came upon the idea.
The potter was in the process of making a highly decorated plate, and was slowly turning the plate in a step-wise fashion, making use of a type of comb to stamp radial dots into the plate.
The horologist came upon the idea that each prong could signify a different note, and whether it was played or not.
After some experimentation, a simple and reliable implementation of this idea successfully entered the market.