Some psychologists explain humans' interest in music with reference to our pattern-finding and puzzle-solving nature. When you hear a certain harmony, there is a mathematical relationship behind it which may sound appealing because of the way it makes our brains react. The various musical scales are usually explained with a mathematical relationship between one note and the next. Furthermore, rhythmic patterns can generally be expressed mathematically, too. The more complex the musical work is, the more complicated the maths you would need to explain it.