One of my favorite Genesis songs. And yeah, I'm an old-school Genesis fan and this is one of the "later" songs, but I don't care; good music is good music.
I still remember putting this album on for the first time, and "Mama" is the first song. There was this low hum coming out of my speakers, and I thought that my ancient stereo was finally dying, and I was bummed. Turns out it was a low E, part of the song, that I'd never heard before, because I'd only ever heard the song on MTV, and our crummy old TV speakers could never reproduce that low E. Once I figured out what was going on, the song went from good to great.
Trivia: There is exactly one cymbal crash in this song.