Can't resist jumping in again. Richard Feynman used to say that you can't really answer a "why" question because it leads to another "why" question. So I'll try to answer the first level question: why do some combinations of notes sound GOOD and some sound dissonant? the answer goes back to Pythagoras( yes, the triangle man) in about 600 BC: the intervals that sound "good" to the ear are ones in which the ratios of the length of the string that makes that note are SMALL WHOLE NUMBERS. Wyo, take your guitar and measure the length of the string, nut to bridge. You will probably get somewhere around 24 inches. (I'm going to use 24 ' for the examples; I have a very old small-scale Martin) Play a note, any note. That is the full length of the string, all 24 inches. Measure off exactly HALF that length and play that note. You should get the same note as before, an octave higher. (That should sound GOOD to your ear) If you go 1/3 the length down, you will get a fifth above (if on 1st string, you will get E, E octave, B) if you go 1/4 the length down you should get A. . . but if you go 13/32 of the way down you will get a note that sounds dissonant ("not as good") when played with the original note. If the ratio of the lengths is a "small" number, it will sound good, if higher, it will sound dissonant. (Hey, this would make a great science project, keep making the ratio a little bigger and see where it starts to sound 'bad". To me 4:3 sounds good and 5:4 sounds less so and by 6:5 it's a definite dissonance.) And you will notice that all we have done is make the "why" one step down-- why do the small whole numbers sound good and larger ratios sound bad? I don't think anybody knows except to say that God must be a mathematician. Was this sufficiently confusing? PETE