Tash said:The simple answer is that they use different tonal and intonation systems in different cultures around the world. There are 11 unique tones in a "scale" in western music (11 half steps). In other tonal systems they divide the same "distance" into 9, or 18, or 21 distinct intervals.
This is why much eastern music sounds "out of tune" to western ears.
Obviously you can make this answer much more complicated if you want to.
there are even a few cultures with non-harmonic music, which sounds extremely strange.
personally, to my ears anything except an even-tempered instrument sounds off. this isn't always a bad thing though.

