Here's an interesting twist. The UK-based on-line classical music store, Presto, which used to provide silver disks, now also operates an excellent internet-based service for classical music. Music can be streamed, but also can be downloaded as files. Why is this important? Well, the very word streaming denotes an internet service which prioritizes timeliness over accuracy. How does it do this? If need be, it just drops packets from the stream. With a bit of luck, the beat remains intact even if some of the music is missing.
A file download over the Internet, on the other hand, will be bit perfect. Any packets which have errors are re-transmitted until they are error free. That's how computer programs (executable files) manage to still work without additional bugs after being downloaded.
How do we know a packet of data has errors in it? Extra data is added, first with a simple parity bit so every computer word plus its parity bit has, say, an even number of bits. If one bit is wrong, it is detected. Now add a second parity bit (imagine at right angles to a 'square' set of words) and now you can detect when two bits are wrong and correct every single bit error.
CD takes this a massive step further. Instead of adding a few error detection bits, the actual content is expanded to about 8 times its size by Reed-Solomon error correction code. This can detect and correct about 4000 consecutive bit errors. Early demonstrations showed CDs playing flawlessly with an 1/8 inch hole drilled through them.
But wait, there's more! CDs don't actually have holes punched in them as the article suggests but are designed to be stamped out by record companies just like vinyl records. So the record company stamps out what it hopes will be the required number of disks. If they sell out, it can stamp out another batch, or just delete the issue from its catalogue. A much later development allowed PCs to use a laser to 'burn' pits in a blank disk, giving rise to copying at the silver disk level. Now Presto and Decca are offering to provide Decca's back catalogue through a burn-on-demand service, delivering silver disks. Brilliant!
Me? I generally buy SACDs - remember these are multi-channel megahertz recordings which Philips and Sony invented to replace CDs about 25 years ago. I stream the CD quality version to see if I like the performance before ordering the silver disk. I am not aware of any service that streams in SACD quality.
As we should all know by now, the internet is not always available.