Do 多音字 usually develop as separate words that just happen to be written in the same way? Or do they usually arise as one word that diverges into different pronunciations for its different senses? This second possibility happens in English: permit is a verb, while permit is a noun, for example. They clearly come from the same word but as different parts of speech are pronounced differently because of prosodic tendencies.
Examples in Chinese I am interested in: 重zhong4 vs. 重chong2, 还hai2 vs. 还huan2.