I've noticed something lately about the music I've been listening to. I sometimes put one of the music stations on the radio. But when I'm listening to something other than the radio, it's almost always one of two things barbershop music, either quartet or chorus, on my MP3 or Los Panchos (or El Trio Los Panchos) on CD.
Once I noticed that, it started me thinking about why. And I realized it was because of the harmony in both. Nearly every note sung is in harmony a chord. And then I realized the same thing, the harmony, is what's driven a lot of my musical preferences over the years, including in my preferences in instrumental music.
Listen to the harmonies for yourself (on YouTube) here's a song called La Hiedra by Los Panchos and God Bless America by Albuquerque's New MexiChords barbershop chorus. The harmonies in both are indeed excellent.