I'm reasonably certain that a mix tape is considered "fair use". (Around the time of PMRC they tried to put a tax on blank cassettes, I don't know if that was going into a fund for artists or just another levy.)
Since sharing Spotify lists is an actual Thing, I'm also reasonably certain that's also fair use.
I'm guessing that, while it may technically fall under something similar that says you're not supposed to play a store-bought DVD on an oil rig without paying royalties, my sharing music with my wife's non-profit lab is not 100 percent kosher - but it's probably 99 44/100 percent pure. I would be happy to kick in to the RIAA or ASCAP, but I'm sure it would be a poultry amount.
As I have been seeking (and sometimes offering) assistance on this Board for over a decade, and I don't think I've ever once posted a "How do I bootleg something" post, I'm going to suggest that I have not flown the coop on this one, and you can presume innocent intent.
When I put together the list of appropriate music from my (purchased) library of over 2,100 records and 1,000 CDs, I found some songs that weren't on Spotify.
So I was wondering what other ways people shared music with their peeps.