Updated: Nov 1, 2019
Remember those 40 second or so intros in songs from the 70s, 80s, or 90s? They are beautiful and set the tone for the song lyrics and the melody that is about to follow.
Nowadays, they're almost gone. It has to do with attention span. The next song is only one click or swipe away. We need the kick immediately, we simply don't take the time to listen to a full album, no matter what. Songwriters and producers pay close attention. This is why intros are mercilessly shortened or skipped.
A few seconds, four instead of eight bars is the max.