I'm not sure. Adjectives like warm (or maybe smoother and less brittle) usually mean less high end, but I don't think that's all there is to it. I think part of

I'm not sure. Adjectives like warm (or maybe smoother and less brittle) usually mean less high end, but I don't think that's all there is to it. I think part of it may be good mastering without overcompression or clipping, and good instrument tone and arrangement (and probably equalization) - with discernible bass, midrange, and highs (though cymbals and high end can get sanded off with repeated plays I guess.) Better playback systems (vs. bluetooth speakers etc.) may also be helping. The number of tracks and stereo image might be helping. And maybe there's some kind of synergy between vinyl-era popular music and its recording media - bands that sounded good on vinyl probably sold more records, etc. On the other hand, I am sometimes blown away by the dynamic range of good classical CDs. Also: has FM radio gotten worse in sound quality?