I don’t download full albums, just individual songs I like.
The sources are basically anywhere I hear music, but generally, it’s by listening to radio.
As of now, this has already got me to 1,179 songs with 3 in queue to be downloaded. (If you’re curious, those in queue are: Dana International - Diva; New Kids On The Block - Step By Step; Prince - Purple rain)
It is hard to call it discovery in this case, more like a reminder of the songs since I knew them already.
Other sources include, but are not limited to: Browsing YouTube playlists, searching for artists to see if they have more good songs, buying a CD compilation, searching for someone’s Spotify playlist after peeking into their phone when I liked multiple songs (they didn’t want to share the playlist, but left it “public”), Bus Simulator Ultimate (there I discovered 2 artists, Melihcan and Cem Kılıç), old tapes, bus driver with a Bluetooth speaker (and me with Shazam), parts of songs randomly appearing in my head from who knows where, background music in videos.