If you do a Google search for your desired music, you might find it.
For example, "Best of Broken Cup and the Clumsy Oafs Mp3 Free Download". You will still get Amazon and other sites trying to sell you a CD of that title, but there might be a Russian site offering it for free - in the format you want. The Russian site do not last long - a month to 6 weeks and then they are gone. But another one soon appears.
They keep disappearing because what they are doing is illegal. It is a moral issue. People see it as victimless, but of course every download is depriving the copyright holder of an income.
There are also "YouTube Converters", which function on-line. Find the YouTube you want, copy the URL, past it into the converter, wait the length of time of the recording, up pops a Download Button, click on it and download, straight to your stick.
Young people do this all the time. 10 get together and all put in a £1. One buys a download album and then shares it to the other 9. Nobody feels guilty, because they have paid, but of course, the author is out by £90.
I am not saying that people shouldn't download music for free, but I am saying that people should be aware that there could be consequences.
Regards
Chas