I was replacing my cassettes with CD's back in the 90's.. I held on to the CD's over the years and then copied them to an iPod.
More recently, I visit the thrift stores and 'antique' stores and look for the old CD racks loaded with old CD's..
Been able to find a lot good ol' stuff that I like for like $2 a CD.
Even Walmart has those $5 CD bins and I've found a lot of stuff that works for me..
Got some 1900 songs on my old iPod that I just plug into the truck with a USB cable and that's what I listen to now.
I still find some stuff here and there, get some stuff off of itunes as the mood strikes..
I still have my old Walkman too! ha, ha! Even a couple of tapes, but have not used tried them for years..
Good luck!
Mitch