The piano keyboard contains all the notes we're likely to be interested in. From C to shining C, an octave contains 12 notes:
7 of 'em are Do Re Mi Fa So La Ti (nevermind that last Do)
5 of 'em are those black keys.

88 keys divided by 12 tones = 7.33 octaves available on a piano.

Not many people can sing all that. But "octave" is just the distance from any note to it's next instance...maybe C to C, or maybe F to the next highest F. So it's hard to say how many there are...kind of like saying "how many inches are there?"

The science behind the vibrations that make these sounds is fascinating to me. If you pluck one guitar string, you have a tone. If you press that string down at its exact midway point, you hear the same tone one octave higher. It's like if you cut it in half, you get twice the vibrations, and twice the pitch. The faster the vibrations, the higher the pitch.

http://www.soundclick.com/MarkKaufman