now you got me worried...
Terra as far as the harmonic series... there's this
http://en.wikipedia.org/wiki/Harmonic_series_(music) which can get a little heady...
I like this pic of a string vibrating:
Let's say that string was the low E string on a 4 string bass. The top string in that pic would be the whole string vibrating and that would give you the main "E" sound, that's the fundamental. The one under that is the string vibrating in two equal halves. Sometimes you can even see that, and it gives you an E but an octave up. The next one is weird, it's the string vibrating in 3 equal parts, and that gives you a B note.
When you mix, getting the fundamentals strong, especially on the bass, without getting the next two harmonics too strong is important. Otherwise it will sound boomy, and all that extra boominess will stop you from being able to get your tracks sounding clear.
You can hear cars with crappy subwoofers and the song is supposed to be have an E note in the bass, but because the system is so junk it actually puts out the 3rd harmonic, a B louder than the low E.
Playing a trumpet or trombone is one of the best ways of learning about the harmonics series.
Stuff like the names of notes and chords is man made, made-up stuff. But the harmonic series is real life physics. You can hear it when dogs make funny sounds. Scientists say it is keeps the planets in their positions.
This is salt on a table being vibrated at different frequencies: