Before the current "equal temperament" system there was a "just temperament system" that basically harks back to Pythagoras. The main intervals in the C scale a

Before the current "equal temperament" system there was a "just temperament system" that basically harks back to Pythagoras. The main intervals in the C scale are very close to whole fractions of low numerator and denominator. The problem is that this doesn't work very well in every key. So the emergence of modern music came with a few tries at averaging these things out until equal temperament in the log scale arose. Some of the character of older music is actually lost because of this. But hey, now all keys work the same.