Oh hey, sorry I just remembered I never replied to this.

If you have a song in mind that you can't find anywhere - which definitely happens sometimes, no matter the artist - then you can always grab a copy to keep locally as long as they have it streaming somewhere eg Spotify, YouTube, SoundCloud, etc. The quality will only be whatever the streaming provider offers, but it's usually good enough if it's nowhere else.

So for instance YouTube has heaps of easy to use downloader apps such as Grayjay, yt-dl/yt-dlg on desktop pc. Or if on android there's 'yt-dl kivy' on the IzzyOnDroid repo for F-Droid, or Grayjay, or Gyawun Music.

If you need advice for downloading from specific platforms there are plenty of Lemmy communities that have knowledgeable people like the piracy community on dbzer0. This is their wiki - https://wiki.dbzer0.com/piracy/megathread/music/

P. S. its not a bad idea to download streaming files only from a VPN by the way, just in case you get your IP blocked by the service (very rare and usually temporary, but i thought I'd mention).