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Comment by Jedd | Hacker News Reader

This specification anomaly sounds like the polycarbonate equivalent of vinyl's multiple-groove capability. [0]

I'd first heard of this for a Monty Python record (wikipedia notes this is in fact the most famous use case) but checked to see if people went for >2 grooves, and seemingly they did. I expect the casting for the pressing was horrendously expensive, which is why it didn't happen an awful lot.

I suppose both mediums shared the less-well-hidden feature where a long silence separated the penultimate from the ultimate track.

[0] https://en.wikipedia.org/wiki/Multisided_record

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When I was very young, my parents had a game called 'wacky races' that was based on a multi-groove vinyl. It was a horse-racing game - I can't recall exactly how the gameplay worked, but the vinyl contained racing calls where the races would start the same way but the outcome would be somewhat random depending on which groove the needle ended up following.

Techmoan has a video on a similar horse racing game (maybe it's even the same just with a different name) and how it works: https://www.youtube.com/watch?v=I5l75romOXY

This is supremely cool, thanks for sharing. I'm probably missing something obvious but why would the casting be any more expensive than any other pressing?

Not terribly informed about the pressing process, but as I understand it, it is (or was) effectively a player-process in reverse.

A needle creates the groove(s), replete with bumps for sound, in a not-quite-set (slightly soft) master disc - and I _speculate_ those follow a specific path defined by the mastering tool.

In comparison, playback just drops the needle in the track, and it necessarily follows the extant spiral form.

Making the master of a multi-groove record I'm assuming would require recalibration of the groove-defining mechanism (doubtless carefully designed for conventional layout), once for each of the grooves you want to make, ensuring they each stay within the boundaries defined by the previous grooves.

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