How to get around "Policy, Signature, Key-Pair-Id" values for a URL?

I am trying to download music from a website, and in Chrome Dev tools, I find that the website is sending the audio file in parts.
I opened one particular part's URL in a new tab and it reads something like this:
something.com/?Policy=(large string no1)&Signature=(large string no2)&Key-Pair-Id=(large string no3)

Also, when I try to remove these parameters and try to access the URL directly, it is forbidden.

My questions:
1] What are these "Policy, Signature, Key-Pair-Id" values for a URL?
2] How do I get around this feature to access the content directly?
3] Can the answer be found by reading the website's javascript files? Exactly what should I be looking for (if you can say)?

Thanks in advance.

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